The coefficient of 6x is
a.6
b. x
c.1

A.6 
because a coefficient is the numerical constant quantity placed before and multiplying the variable in an algebraic expression. (eg 5x so the coeff is 5)

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