Answer:
The text itself determined how to solve the problem.
Namely, two object are given in two relations and we conclude that we have two variables that we present with two equations.
We will take hardcover books as x and paperbacks as y.
First equation is 4x+10y=64
Second equation is 5x+7y=58
This is system of two linear equations with two variables
To solve this system we will use Gaussian agorithm with which we make
gradual elimination of the variables.
We will multiply first equation with number 4 and second with number (-5)
and get
20x+50y=320 and -20x-28y=-232
When we add first equation to another we get
variable x is eliminated
50y-28y=320-232 => 22y=88 => y=88/22=4
y=4 when we replace variable y in the first equation before multiplying
we get 4x+10*4=64 => 4x+40=64 => 4x=64-40 => 4x=24 => x=24/4=6
x=6
Total charge for hardcovers is => 4x+5x=9x=9*6=54$
Total charge for paperbacks is => 10y+7y=17y=17*4=68$
Good luck!!!
Step-by-step explanation:
