Answer: 4
The given line has a slope of -1/4 as this is the number in front of the x. The general equation y = mx+b has m as the slope. So m = -1/4 is given
Flip the sign to get -1/4 turn into +1/4 or just 1/4
Then flip the fraction (aka reciprocal) to go from 1/4 to 4/1 and that simplifies to 4.
Multiplying the original slope (-1/4) and the perpendicular slope (4) will result in -1.
