Answer:
£110
Step-by-step explanation:
We know how much time it takes for a boiler and a radiator, and we need to know how much it will cost for 1 boiler and 4 radiators. We have an initial cost of £30, and since hes doing a boiler - which we know takes an hour - we can already add £20 for a start of £50.
Now, there are 4 radiators, that take 45 minutes each. We need to use this equation:

We divide by 60 because there are 60 minutes in an hour, and he charges by hour. So:

Now, to find out how much to charge, we need to figure out how much to add to the £50. Since it's £20 an hour, and it takes 3 hours to do the 4 radiators, we need to multiply:

Now we add our totals for a grand total of...

Opposite value would be either changing from a positive to a negative or from a negative to a positive.
Absolute value is always a positive value
A) 7.2, -7.2, 7.2
B) -3.5, 3.5, 3.5
C) 5 1/2, -5 1/2, 5 1/2
<span> y – 2 = 4(x – 3)
y - 2 = 4x - 12
y - 2 = 4x - 12
y = 4x - 12 + 2
y = 4x - 10
y - 4x = -10</span>