Answer:
(1, 3), (2, 6), (3, 9)
Step-by-step explanation:
Dividing the first given ratio by 7 gives ...
7/7 : 21/7 = 1 : 3
Multiplying this by 2 and 3 gives the other ratios you want.
= 2(1) : 2(3) = 2 : 6
= 3(1) : 3(3) = 3 : 9
The equivalent ratios are (1, 3), (2, 6), (3, 9).