I just did the first one but I don't know is it correct
So we know that there are 1000 mL in 1 L. We can set up an equation that allows us to solve for how many bottles are needed in order to empty the 30 L tank:

This equation then allows us to cancel out the units of mL and L, leaving us with how many bottles are needed per tank. Then we multiply straight across to give us:

The question asks us to round up to the next whole number, so
it would take 86 bottles to empty one 30 L tank.
Answer:
x=29
Step-by-step explanation:
3x-13=74
We want to solve for x, so we need to isolate it.
The first step is to add 13 to each side.
3x-13+13=74+13
3x = 87
Then we divide by 3 on each side
3x/3 = 87/3
x= 29