What is the cosine of b in this figure

4/5 it’s adjacent/hypotenuse. If you need to show work to find the hypotenuse:

3^2 + 4^2 = c^2
9 + 16 = 25
c^2 = 25
c = 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

It would take her 20 minutes.