He made 3.75 gallons. There was 1/10 remaining, meaning each tenth was 6 cups. The entire thing is 10 tenths so you do 6(10) to get 60 cups. After converting to gallons by doing 60÷26, you get 3.75.
Answer:
26.25 gallons
Step-by-step explanation:

21000 = 800x
x = 26.25 gallons
Answer:
95
Step-by-step explanation:
80+(200 divided by 2)+(420 divided by 4)=285
285 divided by 3=95
0.10x - 0.08x = 250 - 185
0.02x = 65
x = 3250
Price of boots is represented as x, price of tennis shoes is represented as y.
x-y=44.38
x+y=196.12
Isolate x. (Or y, if you wanted to)
x=y+44.38
x=196.12-y
Set them equal to each other.
y+44.38=196.12-y
Solve for y. Then plug it in to either of the two original equations to find x.
x=120.24
y=75.86
Note: This is assuming that the boots are more expensive than the tennis shoes. If the tennis shoes are more expensive than the boots, then the prices would be switched. I didn't find this clear in your question.