Given:
Let the cost of chocolate bar be 'x'.
[tex]\text{Cost of Peanut butter bar=x+0.07}[/tex][tex]\begin{gathered} 5(x+0.07)+6(x)=6.40 \\ 5x+0.35+6x=\text{6}.40 \\ 11x=6.40-0.35 \\ x=\frac{6.05}{11} \\ x=0.55 \end{gathered}[/tex]
Cost of chocolate bar is $0.55
