Solve equations with two unknowns
Given two equations:
(1) `x + 5y = 12`
(2) ` 3x + 2y = -3`
1st Step: Solve equation (1)
`x=12-5y`
2nd Step: substitute `x` into equation (2) and solve `y`
`3(12-5y)+2y = -3`
`36-15y+2y = -3`
`(-13)y = -3-36`
`y = (-39)/(-13) `
`y = 3`
3rd Step: substitute `x` into 1st step equation
`x = 12-(5times3)`
`x = -3`