Question 144273
If angle DEF and angle GHI are complementary, then the sum of their measures must be 90 degrees, so {{{mDEF + mGHI = 90}}} (eq 1).  You are also given that mGHI is eight times as large as mDEF, so you can say:  {{{mGHI=8*mDEF}}} (eq 2).


Substituting in eq 1, {{{mDEF + 8*mDEF = 90}}} 


Solve for mDEF, and then put that value back into eq 2 to get mGHI.