What is 13000000 x 10^ -7 in standard form

Write numerical coefficient of y² in the expression 2x² - 15xy – 7y²

7. if the value of x varies directly with the value of y, and x = 3 when y = 21. what is the valu y, and x = 3 when y = 21. what is the value of x when y = 105?

If chord ab is congruent to chord cd, then what must be true about ef and eg?