How do i use distributive property and mental math to find 5*198

So what you can do is just simplify your problem down to something much more complex. For example you can put 5x190---> 5x (190+8) and you would simplify 5 into 190 and 8 and then you can get 950 from multiplying 5 and 190 and then by multiplying 5 and 8 you get 40 so you add your answer from 190x5 to 40. So it would look something like this ...

5x (190+8)

5x190=950

5x8=40

950+40=990

To check your answer ...

198x5=990

Is this the whole problem? I have only seen it used with parentheses.

Example 4 (8+3)