The Rule said : an x am = an +m
where a - the base . m, n - exponents or powers.
step 1 Lets to find how many white blood cells contain 1lb of body.
If one lb contain 2.7 x 104 ml and every ml contain 7 x 104 white blood cells, then
1lb contain (2.7 x 7) x 104+4 or 18.9 x 108 white blood cells.
step 2 If 1lb contain 18.9 x 108 white blood cells, then multiplication by number of pounds ( weight) will give the total number of white blood cells.
Find for W = 140 lb : 140 x 18.9 x 108 = 2646 x 108 = 2. 646 x 1011 ( make smaller number by increases the power)