Respuesta :

tracycherry
The easiest way to do this is with cross-multiplication.

4 gallons for 30 plants is written as 4/30

x gallons for 45 plants is written as x/45

Multiply 4 x 45 = 180

divide by 30

= 6 gallons of water
frodofrea
4/30 = x/45
cross multiply 
180 = 30x
divide
x = 6 gallons