Could anybody help me with this 7th grade math

Alaptop computer is purchased for $1350 . after each year, the resale value decreases by 30% . what will the resale value be after 5 years?

He amount of carbon-14 present in animal bones t years after the animal's death is given by p(t)equals=upper p 0 e superscript negative 0.00012097 tp0e−0.00012097t. how old is an ivory tusk that has lost 26% of its carbon-14?

Bob the builder is making 480kg of cement mix. this is made by cement, sand and gravel in the ratio 1: 3: 4