Answer:
A drink costs $1.20
Step-by-step explanation:
Step 1: Make a system of equations
50.40 = 3p + 12d
p = 10.80 + d
Step 2: Plug in p for the other equation
50.40 = 3(10.80 + d) + 12d
50.40 = 32.40 + 3d + 12d
50.40 - 32.40 = 15d + 32.40 - 32.40
18 / 15 = 15d / 15
1.20 = d
Answer: A drink costs $1.20