$\"\"$

The equation is $\"\"$

Let $\"\"$ .

$\"\"$

To find the value of $\"\"$ , substitute x = 4 in the function.

$\"\"$

$\"\"$ (Multiply: $\"\"$ )

The cost of 4 energy bars is 9$

$\"\"$

Find the value of $\"\"$

$\"\"$ (Replace x with 7)

$\"\"$ (Multiply: $\"\"$ )

The cost of 7 energy bars is 15.75$.

$\"\"$

The cost of 4 energy bars is 9$.

The cost of 7 energy bars is 15.75$.