What is the square root of 23 subtracted from square root of 37 divided by square root of 23 added to square root of 37??

recall that (a+b)(a-b) = a^2-b^2. So, you have

(√37-√23)/(√37+√23)

Now multiply by (√37-√23)/(√37-√23) and you have

(√37-√23)(√37-√23) / (√37+√23)(√37-√23)
= (37-2√37√23+23)/(37-23)
= (60-2√851)/14