When it comes to multiplication and division, the rule to go by in terms of significant figures is that the answer cannot have more sig figs than the number with the least number of sig figs.
What this means is that you always need to keep an eye out for the number that has the least number of sig figs because that's how many sig figs the answer must have.
In your case, you have
#7.4/3" "#and #" "12.4 * 0.30#
In the first example, you have
#7.4 ->#two sig figs, 7 and 4 #3 ->#one sig fig, 3
This means that the answer must have 1 sig fig, since that's the smallest number oif sig figs you get for your two numbers.
#7.4/3 = 2.46667 = color(green)(2)#
In the second example, you have
#12.4 ->#three sig figs, 1, 2, and 4 #0.30 ->#two sig figs, 3 and the zero after the decimal
This tells you that the result cannot have more than two sig figs
#12.4 * 0.30 = 3.72 = color(green)(3.7)#