How to do it ,I cannot understand this at all

5)
Equation 1: J/A = 2/7 -> 7J=2A
Equation 2: (J+8) / (A+8) = 2/5 -> 5J + 40 = 2A + 16

Substitute equation 1 into equation 2

5J + 40 = 7J +16
7J-5J = 40-16
2J = 24
J = 12
James present age is 12.

A = (7J)/2 = (7*12)/2 = 64/2 = 42
Andy's present age is 42.

6)
Equation 1: (K-38)/S = 2/5 -> 2S = 5K-190
Equation 2: K/(S-38) = 8/13 -> 13K = 8S-304

Substitute equation 1 into equation 2 to get
13K = 4 (5K-190) - 304
K = 152

Solve equation 1 using K=152

S = ((5x152) -190)/2 = 285

Keith has $152 and Shawn has $285