Question

You use 4 gallons of water on 30 plants. At that rate how much water will you need for 45 plants?

Answer 1

You would use 6 gallons of water to water 45 plants 
4=30  
$\frac{45}{30}$=$\frac{3}{2}$
$\frac{3}{2}$of 4 gallons = 6 gallons

Answer 2

you will need 6 gallons for 45 plants. to find the answer you need to set up a proportion. 4/30=x/45. 45*4=180. 180/30=6