How much would 180 pens cost if bought in boxes of 12,each box costing 5.80?

I think $87 because 12×15=180 so 5.80×15= 87 

First we find the number of boxes we need to buy 180 pens.

# of boxes = Total # of pens needed ÷ # of pens per box

# of boxes = 180 ÷ 12

# of boxes = 15

Cost of 180 pens = # of boxes x cost per box.

We know there are 15 boxes and each box costs $5.80

Therefore,

Cost of 180 pens = 15 x $5.80
Cost of 180 pens = $87