What is the addition property of 28+29+42=99

I don't understand what you're asking for but i have an idea.

first you add the numbers 28 and 29

28 + 29 = 57

so the number 57 is now added to 42

57 + 42 = 99

hope this helped, God bless!

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