Does anyone know how to solve 81 increased to 90?

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?

Two cyclists 84 miles apart start riding toward each other at the samen time. one cycles 2 times as fast as the other. if they meet 4 hours later what is the speed (in miles) of the faster cyclists

For each polynomial, determine the degree and write the polynomial in descending order. a. –4x^2 – 12 + 11x^4 b. 2x^5 + 14 – 3x^4 + 7x + 3x^3