Question

Pedro has twice as many carrots as Martha, who has the same number of carrots as Oliver. If Pedro gives 5 carrots to Oliver, then Martha has 3 times as many carrots as Pedro. How many carrots does Martha have?
a) 10
b) 6
c) 3
d) 2
K) 1

Answer 1

"Pedro has twice as many carrots as Martha:"
p = 2m

"If Pedro gives 5 carrots to Oliver," 
p - 5  (Oliver is irrelevant.)

"then Martha has 3 times as many carrots as Pedro"

m = 3(p - 5)

We know p in terms of m, so substitute it in:
m = 3(2m - 5)

Distribute the 3:
m = 6m - 15

Subtract 6m from both sides:
m-6m=-15
Combine variable terms:

-5m=-15

Divide out -5

m = -15/-5

m = 3

The answer is c) 3