A water tank holds 693 gallons but is leaking at a rate of 4 gallons per week. A second water tank holds 924 gallons but is leaking at a rate of 7 gallons per week. After how many weeks will the amount of water in the two tanks be the same?

Simple

you have: one is leaking 3 gallons per week and holds 256 gallons; whereas, the other one is leaking 5 gallons per week and holds 384 gallons.

Set up both the equations

In y=mx+b form--->>>

y=-3x+256

y=-5x+384

To figure out when they will be equal..set the equations equal to each other(remember to isolate the variable)

-3x+256=-5x+384

-3x+256=-5x+384

     -256        -256

-3x=-5x+128

-3x=-5x+128

+5x+5x

2x=128

x=64

After 64 weeks the amount of water in both tanks will be the same.

Thus, your answer.