Benjamin paid $51 for an equal number of calculators and staplers. Each calculator cost $2.80 more than each stapler. How many calculators did he buy if each stapler cost $3.70?

calculators

The price of each calculator: 3.70+ 2.80= 6.50 dollars

The cost of a calculator and a stapler: 6.50+ 3.70 = 10.20 dollars

The number of calculators: 51.00÷ 10.20 = 5