(15 points)pls help/ Geo hw

1. what is the measure of ∠abc? what is the measure of ∠abd?

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Which is a logical conclusion based on the given information? a. figure abcd is a rhombus by the definition of a rhombus. b. segment ac is congruent to segment dc by cpctc. c. angle acb is congruent to angle adc by the angle-side-angle theorem. d. triangle acd is congruent to triangle cab by the hypotenuse-leg theorem.