How many bit strings of length 12 contain exactly three "1s"

Use the distributive law to multiply. 3(4x + 5y + 6)

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

John used linear combination to solve the system of equations shown. he did so by multiplying the first equation by -3 and the second equation by another number to eliminate the x-terms. what number did jonas multiply the second equation by? 4x-6y=23x+5y=11