Substitution Solve the System of Equations x + 5y = 15 2x-y = 8

Let us determine the value of the unknowns in the system of equations:

x + 5y = 15.

2x – y = 8.

Let us express x through y according to the first equation:

x = 15 – 5y.

Substitute to the second:

2 * (15 – 5y) – y = 8.

Let’s open the brackets for a further solution:

30 – 10y – y = 8.

Let’s perform actions with the coefficients of the variable on the left side of the equation, and transfer the number to the right, while the sign in front of it changes to the opposite.

-11y = 8 – 30 = -22.

The second factor is the quotient of the first one.

y = -22: (-11) = 2.

Find x:

x = 15 – 5 * 2 = 5.