Find the slope and y intercept. y=-5/4x+1

Two variables, x and y, vary inversely, and x=12 when y=4. what is the value of y when x=3?

Zoey made 5 1/2 cups of trail mix for a camping trip. she wants to divide the trail mix into 3/4 cup servings. a. ten people are going on the trip. can zoey make enough 3/4 cup servings so that each person gets one serving? b. what size would the servings need to be for everyone to have a serving?

What is r i 4.5+10r=-6.5 with work pls