Answer: a set of beakers cost $19
A pack of test tubes cost $15
Explanation:
Let t represent the cost of a pack of test tubes.
Let b represent the cost of a set of beakers.
The online store shows a pack of 10 test tubes costs $4 less than a set of beakers. This means that
t = b - 4
In order to fully equip the lab, the school orders 12 sets of beakers and 8 packs of test tubes.
a) the expression is
8t + 12b
b) The school office receives a bill for the supplies in the amount of $348. The equation becomes
8t + 12b = 348- - - - - - - - - -1
Substituting t = b - 4 into equation 1, it becomes
8(b - 4) + 12b = 348
8b - 32 + 12b = 348
8b + 12b = 348 + 32
20b = 380
b = 380/20
b = 19
t = b - 4 = 19 - 4
t = 15