x represents the full tank
so 2/9x+12=2/3x
solve for x
2/9x+12=2/3x
try to convert 2/3 to a commom denomenator (bottom numer )
2/3=6/9
2/9x+12=6/9x
subtract 2/9x from both sides
12=4/9x
mulitply both sides by 9 to get rid of fraciton
108=4x
divide by 4
27=x
it can hold 27 gallons
