Q6. In a triangle if 4LA-3LB=12LC, find all the angles.

Answer 1

you know that
A+B+C = 180
4A-3B = 12C
That has no unique solution, since you only have two equations. But, you do get
b = 240 - 16a/9
c = 7a/9 - 60
So, it will be convenient if A is a multiple of 9. Let's say we want integer solutions.
Since B must be less than 180, 16a/9 > 60 so a > 34
see where that takes you