(t-2)/(t-4)=20/19 这个怎么算呢,还有类似于x/135-x/125=12

(t-2)/(t-4)=20/19 这个怎么算呢,
还有类似于x/135-x/125=12

(t-2)/(t-4)=20/19
19(t-2)=20(t-4)
19t-38=20t-80
80-38=20t-19t
t=42

(t-2)/(t-4)=20/19
19*(t-2)=20*(t-4)
19t-38=20t-80
-t=-42
t=42