Answer:
6 : 12
Step-by-step explanation:
sum the parts of the ratio, 1 + 2 = 3 parts
Divide by 3 to find the value of one part of the ratio
18 ÷ 3 = 6 ← value of 1 part of the ratio, thus
2 parts = 2 × 6 = 12
1 : 2 = 6 : 12
