What is -2-(-7)

Pl explain

Shane can shovel the driveway in 4 hours, but if his sister it would take 2 hours. how long would it take taylor to shovel the driveway alone

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Twice the sum of a number and 4 is equal to three times the difference of the number and 7. find the number.