this question represents an arithmetic sequence problem where you can use this formula: a(n) = a(1) + d(n-1) where 'n' is value you're solving for, a(1) is the initial value, and 'd' is the common difference
The answer is 124 deg. because all the equation is 3x+40=7x-72 and when you solve for x, you get 28. Then all you have to do is plug 28 into the equation 3x+40 and you get 124..:)):