Answer:
$0.43
Step-by-step explanation:
We know that the cost to drink tap subtracted from the cost to drink bottled water equals 918.35. We can model this in an equation:
918.35 = 918.78 - t
t represents the cost of drinking tap for a year.
Lets subtract both sides by 918.78 to isolate the t
-0.43 = -t
divide both sides by -1 to isolate the t
0.43 = t
it costs $0.43 to drink tap water for a year.