You burn 20 calories per minute biking for x minutes and 10 calories per minute walking for y minutes. You spend a total of 90 minutes biking and walking and burn 1300 calories.

Question

Write a system of equations to determine how much time you spend on each exercise.

How many minutes did you spend biking?

Answer 1

Write one equation for total time & one for total calories

x=biking time and y=walking time

x + y = 90 20x + 10y = 1300

solve both equations for y

y = 90 - x y = 130 - 2x

since both are equal to y, they are equal to each other

90 - x = 1300 - 2x

-90 -90

-x = 40 - 2x

+2x +2x

x = 40