At 7 degrees celsius the volume of gas is 49 liters. at the same pressure its volume is 74 ml at what temperature

Charle's law gives the relationship between volume and temperature of gas.
It states that at constant pressure, volume of gas is directly proportional to temperature of gas.
V/T = k
where V - volume , T - temperature and k- constant 

parameters for the first instance are on the left side of the equation and parameters for the second instance are on the right side of the equation 
T1 - 7 °C + 273 = 280 K
substituting these values in the equation 

T = 423 K
temperature in Celcius scale - 423 K - 273 = 150 °C