when multiplying exponents, you multiply base numbers with no exponent (9 and five in this case) and numbers with exponents (10 in this case). 9 X 5 is 45 and 10 to the power of 7 times 10 to the power of 2 is 10 to the power of 9 or 1000000000. 45 X 1000000000 is 45000000000.
