Four more than half of a number is at least nine. what is the number ?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

Find the volume of the solid bounded by the plane z=0 and the paraboloid z=1-x^2 –y^2

Isabelle is mixing red and blue paint to make purple paint she adds 3/10 of a fluid ounce of red to 12/25 of a fluid ounce of blue to make 1 1/30 fluid ounces of purple how many fluid ounces of red paint ounces of red paint will she need to make 3 fluid ounces of purple paint