First of all, we know that a line is 180°. This means if we add the angles of 61°, 57°, and angle y, we should get 180<span>°.

Simplify:

Subtract 118° to both sides:

We also know that all three angles of a triangle add up to 180<span>°. So we have:

Simplify:

Subtract 129° to both sides:

</span></span>
A linear equation has 1 for all exponents on the placeholders
aka the equation is first degree (aka the hightest exponent on placeholders=1) so
it is linear