we know that
1 ft--------> is equals to 12 in
the ramp is 12 inches tall----------> 1 ft tall
A ramp measures------------------> 6 ft long
applying the Pythagorean theorem
c²=a²+b²
where
c-----> 6 ft long
a----> horizontal distance
b-----> 1 ft tall
a²=c²-b²------> a²=6²-1²-----> a²=35------> a=√35------> a=5.92 ft
the answer is
5.92 ft