Q value is the emitted part of an energy ledger. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Thirty minus twenty-four releases six
Initial energy 30 joules minus final energy 24 joules leaves emitted energy 6 joules.
Q=30−24=6J
Fifty minus thirty-five releases fifteen
Initial energy 50 joules minus final energy 35 joules leaves emitted energy 15 joules.
Q=50−35=15J
Eighteen minus eleven releases seven
Initial energy 18 joules minus final energy 11 joules leaves emitted energy 7 joules.