What is the missing reason in the two-column proof?

Solve the equation for x.3(6x - 1) = 12 i've tried doing the math and i can't find out what i'm doing wrong

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

1) you deposit $2,500 in an account that earns 4% simple interest. how much do you earn in eight years?