請指教這數學題

設小數是 x,
則大數是 x + 15 (因為兩數相差15)

(x + 15)/4 - 2x = 5

x + 15 - 8x = 20

-7x = 5

x = -5/7

所以,

大數 = -5/7 + 15
= 100/7

吾係好明..
又話差係15
又話係5
if the difference is 15:
Let x be the larger value
x/4 - 2(1-x/a) = 15
x/4 - (2 - 2x/4) =15
x/4 - 2 + 2x/4 =15
3x/4 - 2 =15
3x/4 = 17
3x =68
x =22 右 2/3

大數=100/7
小數=-5/7