Standard Deviations in Normal Distributions

I have a homework question that is as follows.

In a normal distribution, how many standard deviations above the mean is Q3?

I know that Q3 is 75% and using my Z table I find that Q3 is aprox. = 0.68.

I then used Wikipedia and found a graph that shows that Q3 is roughly .68 * (1)std deviation.

Based on this, I know my answer is .68. I am fairly confident because this is one of the multiple choice options.

Simply having the answer is not enough for me. I need to know what the relation is. How do I determine standard deviation when given only that the distribution is normal?