Which of the following constants can be added to x2 - 6x to form a perfect square trinomial?
a.6
b.9
c.36

You need a number so that  2x = -6  that is  -3 . Now square this number. This gives +9 

Answer is 9

1. 0.3 •4 is the same as 4 groups of 0.32. 7•0.8 is the same as 7 groups of 0.83. it increases by 0.5 every time, so 0.5x4 it increases by 0.9 every time, so 0.9x5. 0.9•12=10.86. 0.47•5=2.35i can finish the next ones in a separate post