Diagrams make explanations a lot easier so I created one, see bottom for the picture.
As GHF are all midpoints, that means the lines that connect them are half of the opposite sides.
CD = 2HF
DE = 2GF
CE = 2GH
As HF is 2x CD, and CD = 24:
HF = CD ÷ 2
HF = 24 ÷ 2 = 12
As DE = 2x GF and DF is 9:
DE = 2 x 9
DE = 18
As CE = 2x GH and GH = 7:
CE = 2 x 7
CE = 14
Hope this helps!