3x-4x+21=15 what is the answer to this question ? and how do i get my answer?

Acar travels at an average speed of 56 miles per hour. how long does it take to travel 196 miles

Find the number of real number solutions for the equation. x2 + 5x + 7 = 0 0 cannot be determined 1 2

Plz determine whether the polynomial is a difference of squares and if it is, factor it. y2 – 196 is a difference of squares: (y + 14)2 is a difference of squares: (y – 14)2 is a difference of squares: (y + 14)(y – 14) is not a difference of squares