What is the Coefficient of 5x4

Determine the number of girls in a math class with 87 boys if there are 25 girls for every 75 boys

Whoever gets this right gets the ! the half life of a soul smelling substance is 4 years. if you have 8 oz of this strange substance, how much of it will you have after 20 years? show work.

1/4x+5=3/4. i can't get access to the answer to this question! and, my request on "contact us" will not go