Step-by-step explanation:
if I can read this right, then we have
DE = 3x + 4
EF = 7x - 6
in total, DF = DE + EF = 28
so,
3x + 4 + 7x - 6 = 28
10x - 2 = 28
10x = 30
x = 3
DE = 3×3 + 4 = 13
EF = 7×3 - 6 = 15
