A 12-V battery requires a total charge of 40 ampere-hours during recharging. How
many joules are supplied to the battery?
Can someone explain what is ampere-hours also, plz.

An "Ampere" is a measure of electrical current. It is equal to one Coulomb of charge passing a point in one second. An "Ampere hour" is one Ampere current running for one hour. Since one Ampere is equal to one Coulomb of charge per second, and there are 60x60= 3600 seconds in an hour, "one Ampere hour" is equivalent to 3600 Coulombs of charge. 40 Ampere hours is 40x 3600= 144,000 Coulombs of charge.

But the difficulty with your question is that "Coulombs" are not a measure of energy. There is NOT a specific amount of energy in "40 Ampere hours".