Solve
x + 3y = 9
3x − 3y = −13
a (−1, ten thirds)
b (1, negative ten thirds)
c (−1, 3 over 10)
d (1, negative 3 over 10)

There are 20 children in the cast of a class play and 8 of the children are boys of the boys 4 have a speaking part in the play and of the girls 8 do not have a speaking part in the play if a child from the cast of the place chosen at random what is the probability that the child has a speaking part

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827