Answer: The pairs of ratios that are not in proportion are (b) and (d).
To determine which of the following pairs of ratios are not in proportion, we need to compare the cross products of the ratios.
Step-by-step explanation: If the cross products are equal, then the ratios are in proportion. If the cross products are not equal, then the ratios are not in proportion.
(a) 8:9::24:27
The cross products are 8*27=216 and 9*24=216, so the ratios are in proportion.
(b) 12:18::18:12
The cross products are 12*12=144 and 18*18=324, so the ratios are not in proportion.
(c) 16:24::20:30
The cross products are 16*30=480 and 24*20=480, so the ratios are in proportion.
(d) 21:6::35:14
The cross products are 21*14=294 and 6*35=210, so the ratios are not in proportion.
Therefore, the pairs of ratios that are not in proportion are (b) and (d).