14. Anna burned 15 calories per minute running for x minutes and 10 calories per minute hiking for y minutes. She spent a total of 60 minutes running and hiking and burned 700 calories. The system of equations shown below can be used to determine how much time Anna spent on each exercise.

15x + 10y = 700

x + y = 60

How many minutes, x, has Anna spent running?

So to solve you have to isolate one of the variables and then use substitution to solve for it.

i am going to use x + y = 60 to rearrange

x + y = 60

y = 60 - x

you then substitute 60 - x into the y value

15x + 10y = 700

15x + 10 (60 - x) = 700

then you solve for x

15x + 600 - 10x = 700

15x - 10x = 700 - 600

5x = 100

x = 20

then, to solve for y, if needed

you would use the x variable to find it

x + y = 60

20 + y = 60

y = 60 - 20

y = 40