What property is m angle PQR=m angle RST then angle PQR cong angle RST

An investment decreases in value by 30% in the first year and decreases by 40% in the second year. what is the percent decrease in percentage in the investment after two years

See attachment below and find the equivalent of tan(∠qsr)

1/2+1/6-3/4 simplify the given expression leaving the answer in improper fraction form.