I work out but they're stronger!

I work out 4 times a week. I do cardio for about 30 minutes. I do dumbell curls, , tricep curls and some other stuff with 10 pound/ 15 pound weights too. doing 15-20 reps a set. Even doing so, my friends are stronger than I am and they don't work out...

like I do. Is there something wrong with what I'm doing? I'm 15 years old by the way-

I don't know how tall you are or how tall your friends are but sometimes the taller a person is the more leverage they'll have. Like you may be stronger then they are but if they have longer arms they can use their leverage in a way that they might seem stronger then they really are.

For example, like if you want to move a rock. If you use a stick as leverage to move the rock it will be much easyer then just trying to move it with your hands.

I hope that made sense... Rofl.

alright first of all you obviously don't know much about working out. there is no such thing as tricep curls. I think the word you're looking for is tricep extensions... and anyways if you want to become stronger do smaller sets, like instead of 15 or 20 reps do 10 it builds stronger muscle better. doing lots of reps is just going to make you toned. and alternate the muscle group you work on for example if you do a few sets of bicep curls go do dips to work on your triceps, then alternate to another bicep workout, then after that switch to another tricep workout and so on and so on. and make sure to consume ATLEAST 30 grams of protein within 30 minutes after your workout. and 1 gram of protein per pound of body weight every day. so if you weighed 170 lbs for example then you would want to eat 170 grams of protein a day. and if you have any more questions just feel free to ask...