A music store is selling compact disc for $11.50 and $7.50. You buy 12 discs and you spend a total of $106. How many compact discs that cost $11.50 did you buy?

Question

asked Oct 26, 2021 44.3k views

1 Answer

Joakim Syk · Answer 1 · 2021-10-30T02:57:26+0000

Answer:

$4\ discs$

Explanation:

Let number of compact disc of
$\$11.50=x$

Number of compact disc of
$\$ 7.50=y$

Total discs
=x+y

$x+y=12\ \ \ ..............(1)$

$Cost\ of\ discs\ of\ \$11.50=11.50* number\ of\ discs=11.50* x=11.50x\\\\Cost\ of\ discs\ of\ \$7.50=7.50* number\ of\ discs=7.50* y=7.50y$

$Total\ cost=11.50x+7.50y\\\\11.50x+7.50y=106\ \ ............(2)$

$Solve\ x+y=12\\\\11.50x+7.50y=106$

$Equation(2)-7.50* Equation(1)\\\\11.50x-7.50x+7.50y-7.50y=106-7.50* 12\\\\4x=106-90\\\\4x=16\\\\x=4$

Number of compact discs having cost
$\$11.50=4$