### Home > A2C > Chapter 9 > Lesson 9.3.2 > Problem9-151

9-151.

Where do the graphs below intersect? You should be able to do these without a graphing calculator.

1. $2x + y = 10 \\x + y = 25$

Multiply the second equation by$−1$ and add the two equations together.

$2x + y = 10\\− x − y = −25$

$x = −15$

Use the x-value to calculate the y.

$y − 15 = 25$

$y = 40$

$\left(−15, 40\right)$

1. $2x + y = 10\\ x^{2} + y^{2} = 25$

Solve the first equation for y and substitute it into the second.