The values here are already converted to percentages of milk, so you can watch the cross do its ordinary work on them. Use the table in section 03 to convert a ratio from a question into one of these percentages first — that conversion is the part the model actually tests.
80% and 40% milk, target 50%
weaker : stronger = 3 : 1
All three values are percentage of milk. Never enter one of them as a water percentage; that is the error the whole lesson warns about.