Answer:
k = 3.
Step-by-step explanation:
k + 4 = 7 Add -4 to both sides:
k + 4 - 4 = 7 - 4
k = 3.
We have:
20-minute bike ride
It takes 4 minutes for him to go a kilometer
k is the number of kilometers Garret has already biked
Number of minutes Garret has already biked:
4k
Number of minutes remaining in Garret's ride
20-4k
4(5-k)
Number of kilometers Garret has left to ride
5-k
Four terms means four products, which are added up.
One term with an exponent: 
One term with a coefficient of five, let's make it a like term: 
One term with three factors: 
One constant: 7
Our expression:
Make a proportion
81/30 = x/600
600/30 = 20
x/81 = 20
x = 1620
Solution: 1620 calories
