Can someone pls show how to do this is with explanation

Alake near the arctic circle is covered by a sheet of ice during the cold winter months. when spring arrives, the ice starts to melt. s(t) models the ice sheet's thickness (in meters) as a function of time tt (in weeks). s(t)=-0.25t+4

Simplify the expression. enter the correct answer.

45 was divided by a power of ten to get 4.5. what power of ten was it divided by? people 4.5