300,000,000 into scientific notation

Which problem could be  solved  by evaluating the expression  7×(−3)7×-3?

Translate this phrase into an algebraic expression. 21 more than twice goran's savings use the variable g to represent goran's savings. need to know fast.

For f(x)=2x+3 and g(x)=x^2- 8 find (f+g) (x)