The least common multiple (LCM) of 5, 6, and 7 is 210.
5 × 42 = 210
6 × 35 = 210
7 × 30 = 210
I think it’s 37 sandwiches if he only sold sandwiches
First you need to get two similar terms to eliminate, I'll do y:
-3x + 2y = 10
-4x - 2y= -10
And then you minus
x = 20
Now you can substitute x in to one of the equations to find y:
-60 + 2y = 10
+ 60
2y = 70
÷ 2
y = 35
So your values are y = 35 and x = 20. Hope this helps!