Answer:
2.7 hours
Step-by-step explanation:
We can use the formula
1/a + 1/b = 1/c
where a and b are the times working alone and c is the time working together
1/8 + 1/b = 1/2
Multiply each side by 8b to get rid of the fractions
8b( 1/8 + 1/b = 1/2)
b + 8 = 4b
Subtract b from each side
b+8-b = 4b-b
8 = 3b
Divide each side by 3
8/3 = 3b/3
2.666666repeating = b
Round to 1 decimal place
2.7 = b
