Question

The ratio of chocolate doughnuts to vanilla doughnuts in a bakery is 5:7, and there are 35 vanilla doughnuts.

The baker wants the ratio of chocolate to vanilla doughnuts to be 1:2.
work out how many extra vanilla doughnut is the baker should make

Answer 1

This is only for the actual title question:

Using the 5:7 ratio, the number of chocolate would be 25.

Since we need 1:2, the baker needs to bake 15 more vanilla donuts, so the ratio 25:50.