Significant figures questions!?!?!?!?

Question

Express the answers to the following calculations in scientific notation. (Type your answer using one of the following formats, 1.2e-3 for 0.0012 and 1.20e+2 for 120.)

(a) 145.75 + (2.5 x 10^ -1)

(b) 79500 / (2.1x 10^2)

(c) (7.0 x 10^ -3) - (8.6 x 10 ^-4)

(d) (1.0 x 10^ 4) x (7.0 x 10^6)

Answer 1

(a) 1.4600e+2

(b) 3.8e+2

(c) 6.1e-3

(d) 7.0e+10