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.