Question

Shiloh is 7 years older than Courtney. Shiloh's age is 13 years less than two times Courtney's age. The system below models the relationship between Shiloh's age (s) and Courtney's age (c):
s = c + 7
s = 2c − 13

Which of the following methods is correct to find Shiloh's and Courtney's age?

Solve s + 7 = 2s − 13 to find the value of s.
Solve c + 7 = 2c − 13 to find the value of c.
Write the points where the graphs of the equations intersect the x-axis.
Write the points where the graphs of the equations intersect the y-axis.

Answer 1

Because both of the equations = s, we can set them equal to each other.

c + 7 = 2c - 13.  Now we can solve for c.  Once you have found c, you can substitute it back into either of the two original equations and solve for s.