a radioactive substance is decay exceptionally at a continuous rate such that it loses 40% of the original amount in 4 years. What percent of the original amount is left in 2 years

I'm marking the brainliest and it's 15 points

Ineed asap. 35 points. in order for two polygons to be similar, two conditions must be met. first, all pairs of corresponding sides must be in proportion. second, all corresponding angles must be congruent. prove that angle congruence is not enough, by itself, to establish that two polygons are similar. do this by describing or drawing two polygons that are not similar but whose corresponding angles are all congruent.

Ihave 9 cowry shells if a dozen eggs(12 eggs) cost 2 cowry shells how many dozens can i purchase