Answer:
see below
Step-by-step explanation:
The equation to determine the work time is
1/a+1/b = 1/c where a and b are the times alone and c is the time together
1/80 + 1/30 = 1/c
Multiply by the least common denominator to clear the fractions, which is 240c
240c(1/80 + 1/30 = 1/c)
3c+8c = 240
11c = 240
Divide by 11
11c/11 =240/11
c = 240/11 minutes
c=21.81818
Approximately 22 minutes
For problems like this we can use algebra to help us, the farenheight 6 hours ago was:
(2xt)-6=-20
We have to balance the sides out, first we minus 6
2xt=-26
Now we can divide by 2
t=-13
We now know the temperature 6 hours ago was -13
1. a(x+b)
2. ax+ab
example:
2(x+3)
=2.x + 2.3
=2x + 6