You baked 42 chocolate cupcakes and 28 red velvet cupcakes. you package them in boxes that have the same ratio of chocolate to red velvet cupcakes. how many red velvet cupcakes are in a box that has 24 chocolate cupcakes?

There are 16 red velvet cupcakes.

42 chocolate +  28 red velvet = 70 cupcakes
(42/ 70 *100%)+ (28 / 70 *100%) = (70/70 * 100%)
60 % chocolate + 40% red velvet = 100% cupcake

24 chocolate    +  X red velvet  =  Y cupcake

Y cupcake = 24 / 60% = 40 cupcakes
X red velvet = 40 cupcakes * 40% = 16 red velvet.

OR

(24 / 60%) * 40% = 16 red velvet cupcakes