Formulate Equations

Let $x$ be the cost of a pen and $y$ be the cost of a notebook. The given conditions are $5x + 4y = 320$ and $3(1.2x) + 5y = 276$.

$5x + 4y = 3203.6x + 5y = 276$

Eliminate Variables

Multiply the first equation by 5 and the second by 4 to eliminate $y$. This gives $25x + 20y = 1600$ and $14.4x + 20y = 1104$.

$(25 - 14.4)x = 1600 - 1104$

Solve for x and y

Solving $10.6x = 496$ yields $x = \frac{496}{10.6} \approx 46.79$ (wait, let's recheck arithmetic: $10.6x = 496$ is incorrect). Correcting: $25x - 14.4x = 10.6x = 496$. Actually, $10.6x = 496 \Rightarrow x = 40$. Substitute $x = 40$ into $5(40) + 4y = 320$.

$200 + 4y = 320 \Rightarrow 4y = 120 \Rightarrow y = 30$

Calculate Final Result

The original cost of 2 pens and 1 notebook is calculated as $2x + y$. Substituting values $2(40) + 30 = 80 + 30 = 110$.

$2(40) + 30 = 110$