%/100 X is/of 177 IS 60% of the students. so you put 60/100 and multiply 177/X 177X100=17700. Now divide that by 60 and you come up with 28.33. This obviously is not the answer so you add 28 (does not round up to 29) to 177 and you get 205.
A system of equations refers to a number of equations with an equal number of variables. We will only look at the case of two linear equations in two unknowns. The bracket on the left indicates that the two equations are intended to be solved simultaneously, but it is not always used.