x+5=y
x+y=53
solve for x in the top equation
subtract 5 from both sides
x=y-5
take this value for x and plug it into the bottm equation
y-5+y=53
2y-5=53
add 5 to both sides
2y=58
divide by 2
y=29
substitute y back into the top equation
x+29=53
subtract 29 from both sides
x=24