We know that Sun lei bought a laptop computer for $1500 and the total cost, including tax, came $1590.
And we must find the tax rate.
If the total cost was $1590 and the laptop cost was $1500, then the cost of the tax is
[tex]\text{tax}=1590-1500=90[/tex]Now, We must find what percentage represents $ 90 within $ 1500 and that will be the tax rate
[tex]\text{ tax rate}=\frac{90}{1500}\cdot100\text{ \%}=0.06\cdot100\text{ \%}=6\text{ \%}[/tex]Finally, the tax rate is 6%
