請幫忙解決此數學問題

x=26
y=21


y=x-5
x+y=x+(x-5)
=2x-5

the sum of x and y is less than 49,
so the largest value of the sum of x and y is 48 or 47

if 48 is the sum of x and y

x+y=48
2x-5=48
x=26.5

x in not an interger

if 47 is the sum of x and y

x+y=47
2x-5=47
x=26

so, x=26