Evaluate -2a + b for a = -7 and b =-5

9

Step-by-step explanation:

-2a + b

-2 (-7) + -5

14 + -5

9

Insert the variables values in to equation -2(-7)+-5
Simplify
14+(-5)
Which is just 14-5
Therefore the answer is
9

We are given with a tank filling rate of the pipe of 8000 liter per hour. If the other pipe empties the tank in 3 hours, then the tanks has a volume of 8000l/hr * (3hr) equal to 24,000 liters. The answer is just the product of the rate and the time of emptying