Math formula help???

Question

I need a formula and a website to solve this problem. This is what the paper says:

Tunnels have been used hroughout history for various purposes, such as irrigation and transportation.

Boring Brothers, Inc. has a contract to dig a tunnel through a mountain to accommodate 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 it has a piocture of the tunnel being plowed. Crew A is on the left side and is slightly shorter than Crew B's tunnel residing on the right side. The whole mountain length is 2118 meters.

Are these rates reasonable? I need a formula and a website please!!

Answer 1

I dont know the formula but it can be solved.
Crew B starts 2 days after crew A so by then 18 m of the tunnel is dug. 9x2=18
Remaining 2100
Crew A digs 9 m
crew B digs 12 m
Total lenght dug in a day 21
2100 divided by 21 eauals 100
plus the 2 days crew A dug
So total days to dig the tunnel 102

Answer 2

total distance = (CrewA Rate) * Days + (CrewB Rate) * Days
so,
(forget the two day head start for a moment)
2118 = 9m/day * Days + 12m/day * Days
2118= (9m/day +12m/day ) * Days Distributive Property!
2118=21m/day *days
approximate 2118/21 =100 days R18m
So both crews were working for 100 days but Crew A
worked two extra days in the beginning of the problem
9m/day * 2 days = 18 (which clears up the remainder from above!)
The project was 102 days long!

Answer 3

Well im not quite sure i understand what the question is... Do they want to know how long it will take to complete the highway?? If so then the equation is 9x+12(x-2)=2118. And the answer is x=102 days.