Question

1.8X + 3y = 3, -2x - 2.5y = -5

Answer 1

Given the system of equations:

`\begin{gathered} 1.8x+3y=3\text{ } \\ -2x-2.5y=-5 \end{gathered}`

Multiply the first equation by 2.5 and the second by 3 to eliminate y

So,

`\begin{gathered} 4.5x+7.5=7.5 \\ -6x-7.5y=-15 \end{gathered}`

Add the last equation :

`-1.5x=-7.5`

Divide both sides by -1.5

`\begin{gathered} (-1.5x)/(-1.5)=(-7.5)/(-1.5) \\ \\ x=5 \end{gathered}`

Substitute with x = 5 at the equation 1.8x+3y=3

`\begin{gathered} 1.8\cdot5+3y=3 \\ 9+3y=3 \\ 3y=3-9 \\ 3y=-6 \\ y=-(6)/(3) \\ \\ y=-2 \end{gathered}`

So, the solution of the system

`\begin{gathered} x=5 \\ y=-2 \end{gathered}`