She is correct because a negative subtracted by a negative is positive.
Let numbers of books be 'b' and numbers of CDs be 'c'
We can set up two equations:
Equation [1] ⇒

Equation [2] ⇒

We are solving for the number of books and the number of CDs bought
When we have two equations in terms of two different variables;

and

, that we need to solve, then this becomes a simultaneous equation problem.
First, rearrange Equation [1] to make either

or

the subject:


Then we substitute

into Equation [2]






Now we know the value of

which is

, substitute this value into

we have

Answer:
Numbers of books = 13
Numbers of CDs = 7
Answer:
x<8
Step-by-step explanation:
2x+5>3x-3
2x+8>3x
8>x
Answer:
15/164
Step-by-step explanation:
5/8 ÷ 6 5/6 = 15 / 164