Answers to questions 15,19,20,21 &25

The answer to your question is below

Step-by-step explanation:

15. x² = 144

    x = √144

   x = ± 12

19. 9x² = 4

      x² = 4/9

      x = √4/9

    x = ± 2/3

20.

      25y² = -16

          y² = -16/25

          y = √-16/25

          y = ± 4/5 i

21. 16y² = 25

        y² = 25/16

        y = √25/16

        y = ±5/4

25.

       81 - 9x² = 0

       81 = 9x²

       81/9 = x²

         9 = x²

       √9 = x

        x = ± 3

i know the answer is 3

step-by-step explanation:

72 fudge and 75 toffee

step-by-step explanation:

i hope this : )