How do I use Brainly math for solving stuff like this and how do I show my evidence on paper?

Answer:
a) 3
b) 1/3
Step-by-step explanation:
I've never used Brainly math before, but I can help you out with the work for these problems.
Part A
3(x + 1) - x = 15
3x + 3 - x = 15
4x + 3 = 15
4x = 12
x = 3
Part B
5(x + 2) - 2x = 11
5x + 10 - 2x = 11
3x + 10 = 11
3x = 1
x = 1/3
Hope this helps!