Need 22 and 23. i start school tomorrow

Asystem of equation is shown below 6x - 2y equals 3 . and 5x + 3y equals 4. would you solve by substitution or elimination? and why

Which of the following is the equation that says that the product of a number and ten is equal to 20 percent of that number ? a) 10n= 2.0n b) 10+n=.20n c) n+ .20n=10 d) 10n=0.20n

What is the number 321,000,000 in scientific notation? also what is the number? ?