How do I solve the problem below?

Question

How do I solve this:

Find a whole number a such that the numbers 2/a, a/5, 82% are in order from least to greatest. a=

Answer 1

2/a < a/5

if a>0, then cross multiplication says: 10 < a^2 ---> sqrt(10) < a

so for example , a=4 satisfies this condition, since sqrt(10) < 4.

So then 0.5 = 1/2 = 2/4 < 4/5 = 0.8< =.82=82%

But if a<0, then 2/a < a/5 ---> 10 > a^2 ---> sqrt(10) > a

So for example a=3 satisfies this condition since sqrt(10)>3

then -2/3 = -0.6 < -0.6 = -3/5 < +82%

Note that a cannot be zero: