Let L = Larger and S the smaller
(3/8)L - 10S = 5
L = 8S + 48/5
Clear fractions and rearrange terms
3L - 80S = 40
5L - 40S = 48
Double the 2nd equation
3L - 80S = 40
10L - 80S = 96
Subtract the first equation from the 2nd
7L = 56 and L = 8
5*8n- 40S = 48
S = -1/5
You should take these answers and plug them back into the original problem to be sure they are correct.