In ARST, measures of ZR, ZS, and ZT are 90°,55°, and 35° respectively ( = 90, 6 tan(35)
8
tan(35)
15

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.