Answer:
slope = 7
Step-by-step explanation:
You have that the plane y=1 intersects the following surface:
(1)
To find the slope of the curve, you first replace y=1 in the equation (1):
(2)
This is the generated curve when the plane y=1 intersect the surface z.
The slope of a function is given by the derivative of the function. Then, you calculate dz/dx in the equation (2):

The slope only depends of the value of x. The slope for the point P(1,1,2) is:

The value of the slope of the tangent line to point P is 7