Help .
i need help with something like this

The width of a book is 1.5 inches.
The total width of 79 books is 1.5×79
= 118.5 inches.
The cost of a 34.5 inch wide shelf is $12.95
Therefore, the cost of a 118.5 inch wide shelf will be:
(Let the cost of the 118.5 inch wide shelf be x)
[tex] \frac{34.5}{12.95} = \frac{118.5}{x} \\ cross \: multipy \\ 34.5x = 118.5 \times 12.95 \\ x = \frac{118.5 \times 12.95}{34.5} \\ x = 44.48[/tex]
x= $44.48