Can someone help in need the length of the third side

During a bike challenge riders have to collect various colored ribbons each 1/2 mile they collect a red ribbon each eighth mile they collect a green ribbon and each quarter mile they collect a blue ribbion wich colors of ribion will be collected at the 3/4 markrer

What is the measure of angle x? answer

Find the domain and range of the following function f(x) = 51x - 21+ 4