(7X10^-21)/(7.6X10^-22) is equal to:
(7/7.6)(10^-21/10^-22)
Rule for division of similar bases with exponents...
(a^b)/(a^c)=a^(b-c)
In this case we have (10^-21)/(10^-22)=10^(-21--22)=10^1
And 7/7.6≈0.921, and we only had two significant figures so 0.92 works
0.92X10^1
9.2
So the half life of helium-9 is about 9.2 times greater than the half life of helium-5
