For every 3 bottles of water sold at a gas station, there are 4 bottles of soda sold. if there are 20 more bottles of soda sold than water in a day, how many bottles of water were sold?

A) w / s = 3 / 4  OR A) 4w = 3s

B) w + 20 = s then multiplying B) by -4

B) -4w -80 = -4s  then adding it to A)

A) 4w = 3s

-80 = -s

So 80 bottles of soda and

60 bottles of water were sold

DOUBLE-CHECK

60/80 = 3/4 and 80 -60 = 20  correct!!

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.