### Home > GB8I > Chapter 7 Unit 8 > Lesson INT1: 7.1.7 > Problem7-82

7-82.

Apollo and Zeus are Great Danes and are both on diets. Apollo, is still a puppy and needs to gain weight. He currently weighs $75$ kg and is gaining $2$ kg per month. Zeus is an older dog who needs to lose weight. He currently weighs $130$ kg and is losing $3$ kg per month. In how many months will they weigh the same? Does your solution make sense in the context of this problem?Homework Help ✎

Use a system of equations ($2$ equations), where
$x =$ number of months and $y =$ weight in kg.

When writing the equations use slope-intercept form
($y = mx + b$). Where $m$ is the rate of change and b is the starting weight.

Equation for Apollo is $y = 2x + 75$.
Equation for Zeus is $y = -3x +120$.

Use the equal values method to solve the system.
So $2x + 75 = -3x + 120$. Solve for $x$.

$x = 11$ months