Evaluating a function means to plug the required value, substituting every x occurrence with that value.
So, you have
Subtract the two equation from each other
-3x-7y=-66
-10x-7y=-24
--------------------
7x =-42
x=-6
by substituting in equation 1
(-3)(-6)-7y=-66
18-7y=-66
-7y=-84
y=12
so to check we substitute in the first equation
(-3*-6)-(7*12)=-66
18-84=-66
-66=-66
we check the second equations
-10(-6)-7(12)=-24
60-84=-24
-24=-24
Answer:
<em>The answer for both of them is going to be zero</em>
If all my calculations are correct Helen should make £700. If she has a 3:1 ratio that means she has 3 times as many fiction books as she does nonfiction. This means out of Helens total 80 books, 60 would be fiction and 20 would be nonfiction. Now to calculate the price, all the fiction books are £10 so that would give her £600. All the non fiction books are £5 and so that would give her £100 and then combined Helen should have £700
Here's the graphical solution.
... (x, y) = (1, 0)
