Find the sum and express it in simplest form. (ab+4a-6)+(ab+6)

Icould really use some with this question.

Ascientist has 50 grams of a radioactive element. the amount of radioactive element remaining after t days can be determined using the equation (1) after two days the scientist receives a second shipment of 50 grams of the same element. the equation used to represent the amount of shipment 2 remaining after t days is 10) - 50 which of the following is an equivalent form of the expression for the amount remaining in shipment 2? what’s the answer?

Maria solved an equation as shown below. what is the solution to maria’s equation?