The angle of elevation of a ladder is 19∘ and the ladder is 12 feet from the wall. what is the height of the ladder in feet?

Can someone explain the elimination method to me for this problem?

If private savings 'v' = 0.75s and total savings 's' equals $4.20 billion, solve for public and private savings.

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.