i need to make c the subject in this formula? any help would be nice please.
Now, t, in s= c+ mt is not "by itself" is that two things have been done to it: to get to "c+ mt" from t, you would "multiply by m" and "add c" in that order. To "undo" it, do the opposite things in the opposite order: first "subtract c" then "divide by t".
From s= c+ mt, subtracting c from both sides gives s- c= mt. Now divide both sides by m- but be sure to show that the entire right side, s- c, is divided by m, not just "c": use parentheses (s-c)/m= t, not "s- c/m" which means s- (c/m)!