Constants are necessary in a controlled experiment because without constants you would not know which variable affected the?

Iam on that question know can you tell me the answer i am realy strruglingasap

If one were to put the y value into the equation, they could find out what x is for a certain value of y.  putting in the value of y (1), we get the equation: 1=4x-12=4xx=0.5this means that the value of x when why is 1 is x=0.5

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2   where t1=temperature of cold reservoir ( ° k) = 135            t2=temperature of hot reservoir ( ° k)   = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58%  note: this is the theoretical maximum efficiency of a perfect heat engine.   real-life engines do not achieve this value.