Can someone explain how to solve this system using substitution?

Question

1.25x + 0.75y = 109.75
x + y = 105

Answer 1

sure. the 2nd equation says that

y = 105-x.

Substitute that into the first equation to get

1.25x + 0.75(105-x) = 109.75
x = 62
So, y = 105-62 = 43

Answer 2

1.25x + 0.75y = 109.75
x + y = 105 > x = 105 - y

Put x value in the first equation;

1.25(105 - y) + 0.75y = 109.75
131.25 - 1.25y + 0.75y = 109.75
131.25 - 0.5y = 109.75
-131.25 -131.25
___________________________________

-0.5y = -21.5
______ _______

-0.5 -0.5

y = 43

Now solve for x. Use either equation.

x = 105 - 43
x = 62

x = 62