An orange has 20 fewer calories

than a banana. If 7 bananas have

the same number of calories as 9

oranges, how many calories are in a

banana?

90 calories in a banana.

Step-by-step explanation:

O = B - 20 where O is the number calories in an orange and B is a that in banana.

Also 7B = 9O

From the above O = 7B / 9 so substituting in the first equation:

7B / 9 = B - 20

7B = 9B - 180

2B = 180

B = 90.