51.7ml at 27 Celsius and 90kpa to stp

STP is the abbreviation of standard condition for temperature and pressure which is 273.15K temperature and 1.013 * 10^5 Pa pressure. Since the pressure and temperature changes, I assume the question would ask about the result of the volume. The temperature used in ideal gas should be Kelvin, so 27 Celcius would be 300.15K.

The calculation would be

PV=T

V=T/P

V2/V1 = T2*P1/T1*P2

V2/V1=273.15K * 90^10^3Pa / 300.15K * 1.013 * 10^5 Pa

V2 = 0.81904 * 51.7ml

V2 = 42.34ml