Hello!

11 - (3x + 1) = 7(x - 6) + 2
Distribute the coefficients outside of the parenthesis:
11 - (3x) - (1) = 7(x) + 7(-6) + 2
Simplify:
11 - 3x - 1 = 7x - 42 + 2
Combine like terms:
10 - 3x = 7x - 40
Add 3x to both sides to isolate x:
10 = 10x - 40
Add 40 to both sides:
50 = 10x
Divide both sides by 10:
x = 5
Derek would have planted the tree 7 years ago. You subtract 36 from 44.75 and get 8.75. This is how much the tree grew since he planted it. Then, you'll divide 8.75 by 1.25 (1 1/4) which tells you how many years it has been since he planted the tree. The final answer is 7 years. Hope this helps!