Which shows the expression below simplified?
(2.2 x 10^-1) + (2.3 x 10^-2)
hint: you must have the same power of 10 before you can add.
a) 2.43 x 10^-2
b) 4.5 x 10^-1
c) 4.5 x 10^-2
d) 2.43 x 10^-1

Lizette is training for a marathon. at 7: 00 she left her house and ran until 8: 30, then she walked until 11: 30. she covered a total distance of 18 miles. her running speed was six miles per hour faster than her walking speed. find her running and walking speeds in miles per hour.