Can I lose weight by exercising three times per week?

Work out your Total Daily Energy Expenditure, then eat 10-20% less than that, or if you are shooting for Lb/week weight loss, then eat 500 calories less than that. Keep exercising 4x/week, i'd suggest weightlifting as well, but do whatever you like best.
Some dieting tips from personal experience:
Drink lots of water when hungry like 4 L

Eat a ton of non starchy veggies, these are extremely low calorie and you can eat a lot and fill up, I like to cut up capsicum, mushrooms, and whatever else i have lying around and bake it in the oven with garlic.

High protein diets with low calorie dense food are ideal for dieting for a number of reasons, the macronutrient protein isn't as easily converted into fat cells in comparison to the other macronutrients, and eating low calorie dense food is obviously a good thing when dieting simply because you are full on fewer calories. Veggies, rice, chicken, tuna, lean beef

Use appetite suppressors. Caffeine is a great natural appetite suppressor. Just drink more coffee through out the day. Especially when feeling hungry. Another is Ephedrine, which would only be available depending where you lived. In the States Ephedrine is readily available. Ephedrine is one of the most potent appetite suppressors.

Use those really low calorie foods/deserts. I like to eat 7 calorie jello when i diet. I make a big 2 L bowl of it and eat it all, only 7 calories. Diet soft drinks, and all those drinks with 0 sugar and next to no calories are great when you crave something sweet.

Don't be afraid to eat certain foods, or restrict yourself from having fun and going out to eat. Flexible dieting works a lot better than limiting certain food groups. So if you are planning on eating out at night, during the day make sure you have gone very low on the calories so you have a kind of calorie buffer for the big dinner you are expecting. Also don't be afraid to have a treat provided you are still in a calorie deficit. It is pretty easy to eat ice cream every day and still lose weight, just not a lot of ice cream.
- A method i found worked for me, when i craved a certain food and couldn't get it out of my head, but i knew if i were to eat it right then and there i wouldn't be able to stop myself from eating it all and binging, was to schedule a day where i would eat it. On Friday i would allow myself to eat the treat I wanted, while still not going overboard on calories, and the few days wait made me not want the treat as much.

There are a lot of online calculators to work out your TDEE, but use them approximately, you are going to have to track your calories and work out for yourself how much you can and cannot eat to achieve your goals. They are a good start however.

TDEE Calculator
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