The distributive property to find the value of 19·42+19·5819·42+19·58. How to do this mentally

I'm going to assume you put the equation in twice. So you first take the tens place and multiply the an then multiply the ones place together and then add the two products together. 10 times 40=400 and 9 times 2=18. 400+18=418. Now do 10 times 50=500 and 9 times 8=72. 500+72=572. Lastly do 572+418 to get 990.

Using the distributive property in reverse (we usually call this factoring) allows us to pull the factor of 19 out of each term.

19*42 + 19*58 = 19 * (42+58)

Add the stuff in the brackets before multiplying.