Test 2 Section 4 #34 Thanks!!

Let’s say that *d* = the number of hours Doug spent in the lab, and *l* = the number of hours that Laura spent in the lab. Here are the equations we can write from the question:

*l* + *d* = 250

*d* = *l* + 40

This question is begging for a little substitution. Let’s take the expression for *d* we have in the second equation and plug it into the first.

*l* + (*l* + 40) = 250

2*l* +40 = 250

2*l* = 210

*l* = 105