Type the least common multiple of the x coefficients for the following system of equations.

Question

 3x − 4y = 20

7x − 13y = -15

Answer 1

Since 3 and 7 are both prime, the LCM is (3)(7) = 21

Answer 2

Hmm...

The x coefficient in the first equation is 3. Its multiples are 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, ...

The x coefficient in the second equation is 7. Its multiples are 7, 14, 21, 28, 35, 42, ...

Find the smallest number that appears on both lists.