Answer:
Cooper needs 39.8 mL milk for his recipe
Step-by-step explanation:
Let B be the quantity of butter
and
m be the quantity of milk
So according to given statement the whole mixture measures 70.4 mL while butter measures 30.6mL
so,
B+m = 70.4
30.6 + m = 70.4
m = 70.4 - 30.6
m = 39.8 mL
Cooper needs 39.8 mL milk for his recipe ..