FIrst, construct a ratio. Isabelle needs 3/10 red to make 31/30 purple. So, we can divide red by purple to form a fraction to determine how much red paint for 1 fluid oz of purple. (3/10)/(31/30)=(9/30)/(31/30)=9/31. For every 1 oz of purple, we need 9/31 oz of red. Because we found how much red paint for 1 oz purple paint, we simply multiply by 3 to find how much red paint for 3 fluid oz of purple paint. (9/31)*3=27/31
If you want to find out what that number is, then let's call it n n + 3n (Three times the number) + 12 = 32 Simplify 4n + 12 = 32 Subtract 12 from each side 4n = 20 Divide each side by 4 n = 5
