{18-12+8-16/3+...} find the sum

Through non-collinear points there is exactly one plane.

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

Avery’s piggy bank has 300 nickels, 450 pennies, and 150 dimes. she randomly picks three coins. each time she picks a coin, she makes a note of it and puts it back into the piggy bank before picking the next coin.