3/5 = 0.6 = 60%
60% of the total take Spanish.
That leaves 40% for the other languages.
1/4 of 40% is 10% that take German.
40% - 10% = 30% take French.
The slope will be -1/2. If you put it into slope intercept form of y=mx+b, mx will always be the slope.
