I assume you want to know each side length ???

If I'm seeing this correctly, we have

[3x + 4] + [2x + 3] + [ 2x - 9 ] = 75 simplify

7x - 2 = 75 add 2 to both sides

7x = 77 divide by 7

x = 11

So, one side = 3(11) + 4 = 37

One side = 2(11) + 3 = 25

And one side = 2(11) - 9 = 13