Answer or explanation please?

Question

Answer to "Lupe swims two fewer laps than Mary. If both added seven laps to their daily swims the sum of their laps would be three times as many as Mary now swims"

Answer 1

Let L = # Lupes laps now

Let M =# Marys laps now

 

L = M-2  because Lupe swims 2 fewer laps than Mary

 

(L+7)+(M+7) = 3M

because adding 7 to both their current laps will total

3 times as many as Mary does now

 

L=M-2

L+M+14=3M

 

To solve for M, replace L with M-2 in the 2nd equation

 

M-2+M+14=3M

2M+12=3M

M=12

 

L = M-2 = 10

 

Lupe swims 10 laps and Mary swims 12