The usual grading system is percentages. We need to express 25 out of 30 as a percentage. First, we work it out as a fraction: 25/30=5/6 because 5 is a common factor of the top and bottom, so we can divide both by 5. Now we multiply this fraction by 100=5/6×100=5/3×50=250/3=83% roughly. So the grade, under this system, is 83 percent.