It means that the variables cancelled out and you might have made an error in your working, or it could also mean that that solution was not going to work out (hence leading 0=0). It all depends on the question.
Hope I helped :)
You need to first multiply 100 by 42 then divide by 15
-4 next to x value means the graph is moved 4 units to the right
+5 on the end of the function means the graph is moved up 5 units
