Question

The sum of two numbers is 87. if three times the smaller number is subtracted from the larger number the result is seven. find the two numbers

Answer 1

$\left \{ {{a+b=87} \atop {a-3b=7}} \right.$

a-3b=7
a=7+3b

a+b=87
(7+3b)+b=87
7+4b=87
4b=87-7
4b=80
b=20

a=7+3b
a=7+3*20
a=7+60
a=67