Thank you for the opportunity to help you with your question!

Consider the right angle triangle (as not enough information is given)

Slope of hypotenuse = tan x = leg / base

Given: Slope = -3.5

Thus, Leg / Base = -3.5

Now there can be various combination of leg and base values to get a slope of -3.5. Two possible can be -

Leg = 7 , Base = 2, and

Leg = 14, Base = 4

Negative sign in the slope value tells about the angle being obtuse and has nothing to do with the side lengths. Thus both values (7,2) and (14,4) will give a slope of 3.5

Please let me know if you need any clarification. I'm always happy to answer your questions. Kindly best this answer if it has helped you.