Someone help me, i dont get it.

What is the y-intercept of the line with the equation 3x + 4y = 12?

What is the surface area of the sphere?

The perimeter of ? cde is 55 cm. a rhombus dmfn is inscribed in this triangle so that vertices m, f, and n lie on the sides cd , ce , and de respectively. find cd and de if cf=8 cm and ef=12 cm. the answer is not cd=20 and de=15. i have tried that one, it does not work.