how do you solve systems by substitution?

Question

such as:
{ y=x-1
{ x+y=10

Answer 1

The equations is

y = x - 1

x + y = 10

Substitute the y value in eq (1).

x + x  - 1 = 10

2 x - 1 = 10

2 x = 10 + 1

2x = 11

x = 11/2 = 5.5

x = 5.5

Substitute the x value in y = x - 1

y = 5.5 - 1 = 4.5

y = 4.5

Solutions : x = 5.5 and y = 4.5.