Can I have another alternative equation for a different project?

Question

I know that I have already asked for this question before, but I need another equation. This time, I'll just read what it says on the paper:
Tunnels have been used throughout history for various purposes, such as irrigation and transportation.

Boring Brothers, Inc. has a contact to dig at tunnel through a mountain to accomodate the construction of a major highway. Crew A starts at the west end and digs at a rate of 9 meters per day. Crew B starts at the east end two days after Crew A and digs at a rate of 12 meters per day.

Then there's a picture of the tunnel that's being plowed through. On the left side is Crew A. The line is slightly shorter than Crew B, residing on the right side. The total distance of the two teams is 2118 meters. On the paper, it says that I should check to see if these rates are reasonable. Thanks for your help.

Answer 1

Hopefully, you are trying to solve for "how many days has Crew A/B been digging...

That means that in writing your equation, the number of days is your variable...

9(X+2) + 12X = 2118

9 meters per day times the number of days that Crew A has been digging
plus
12 meters per day time the number of days that Crew B has been digging
equals the total distance excavated

Now, all you have to do is solve for X.