Math question need little help

Question

During one month, a homeowner used 500 units of electricity and 100 units of gas for a total cost of $358. The next month, 300 units of electricity and 150 units of gas were used for a total cost of $240. Find the cost per unit of gas

Answer 1

Using E to represent the $/unit cost of electric, and G to represent the cost of gas in $/unit.

500E + 100G = $358

300E + 150G = $240

Multiply the first equation by 3 and the second by 5 to eliminate the E variable.

1500E + 300G = $1074

1500E + 750G = $1200

Subtract the first from the second equation:

450G = $126 G = $126/450 G = $ .28 per unit