2) the distance between the sun and the earth is about 1.5 x 10 to the power of 11m. express this distance with an si prefix and in kilometers.

1.5 x 10^11 m = 150000000000m
1000m=1km

150000000000m x 1km/1000m = 150000000km
1.5 x 10^8km

Explanations can be elaborated by an example:

The scientific notation of 70, 030, 000. To find the scientific notation of this value 
1.  We first move the period which separates the whole number from the decimal number which is located after the numbers of the given value. 
2.  We move it in the very recent order number which is seventy million, seven and zero. 
3.  It becomes 7.003
4.  Thus we count how many moves we did from the tens to the ten million order place. 
5.  7.003 x 10^7