Acity water tank holds 20 gallons of water. a technician empties 25% of the tank. how many more gallons of water must be removed from the tank so that it has 2/5 of the water that it started with?

20
empties 25%
25%=1/4
1/4 of 20 is 5
20-5=15
15 left
how much more must be removes so it reaches 2/5 of 20
2/5 of 20=40/5=8
15-what=8
minus 15 both sides
-what=-7
multipy-1
what=7

answer is 7 more gallons must be removed