Ay = 6, cy = 15, and yd = 4. what is the measure of by?

Me because some of question i don’t understand

The distance from the sun to earth is about 1.5×10 to the 11th m suppose light travels at a speed of 3×10 to the 8th m per second about how long does it take light from sun to reach earth

Your vet has placed your pet on a diet. the diet is to contain at least 12 mg of fat and at least 14 mg of protein per serving. these requirements are to be obtained from two food sources. source a contains 2 mg of fat and 2 mg of protein per serving. source b contains 1 mg of fat and 3 mg of protein per serving. if source a sells for $1.28 per serving and source b sells for $1.12 per serving, how many servings of each type should be purchased to satisfy the requirements at minimal cost?