How do you find the lowest common denominator for 8/15 + 2/12?

Tracy solved the following problem. which of the statements is true? 9 ÷ 3 + 6 × 2 3 + 6 × 2 9 × 2 18 her answer is correct. her answer is incorrect. she should have multiplied before dividing. her answer is incorrect. she should have multiplied before adding. her answer is incorrect. she should have added before dividing.

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

For a function f(x), a) if f(7) = 22 then f^-1(22) = b) f^-1(f(c)) =