There was 300 girls and 400,000,001 boys if we timed it together how much will get

I thing you mean 300 and 400,000,001 timesed together (multiplied)

so you could use a calculator
or

400,000,001=400,000,000+1 so
300 times 400,000,001=(300 times 400,000,000) plus (300 times 1)

400,000,000 times 300= (3 times 4=12, count the zeros and add them togethter)=120,000,000,000

300 times 1=300
300+120,000,000,000=120,000,000,300

D) the x-intercept represents adam's commission pay when he had zero total sales