Name: Systems of linear equations by substitution: solution walkthrough
Uploaded: 2026-11-13
Duration: 1 min 48 s
Description: If y = 2x - 5 and x + 2y = 20, what is the value of y? Try it, then watch the animated solution.

Each equation is a line. The pair

(x, y)

that makes both true is the point where the lines cross.

The first equation says

y

equals

2x - 5

. Put

(2x - 5)

in place of

y

in the second equation.

Distribute the

2

to both terms:

x + 4x - 10 = 20

. Then

5x = 30

, so

x = 6

.

The question asks for

y

. Put

x = 6

into

y = 2x - 5

:

y = 12 - 5 = 7

. Check:

6 + 2(7) = 20

.

Traps:

6

is

x

, not

y

.

5

forgets to multiply the

{-5}

by

2

.

{-1}

subtracts

10

instead of adding it.

Try it first