$13.75 = 3p + 4d
$9.75 = 2p + 3d
Using 2nd equation, divide all factors by 3 to isolate hot dog price and solve in terms of pizza price:
3.25 = 2/3p + d
3.25 - 2/3p = d
Now substitute for d in the other equation:
$13.75 = 3p + 4(3.25 - 2/3p)
Distribute the 4:
$13.75 = 3p + 13 - 8/3p
Combine factors of p:
$13.75 = 9/3p - 8/3p + 13
$13.75 = 1/3p + 13
Isolate and solve for p:
$13.75 -13 = 1/3p
0.75= 1/3p
0.75 * 3 = p
2.25 = p
The price of pizza was $2.25 per slice.
