Answer:
Step-by-step explanation:This is two variables and two equations. x and y will be the two different numbers.
1.x + y =138
2.x= y-20
plug #2 into #1.
(y-20) + y = 138
2y - 20 = 138
2y = 158
y = 79 and plug into #2 and find x.
x = 79-20 = 59 = x