Sun lei bought a laptop computer for $1800.
the total cost, including tax, came to $1890.
what is the tax rate?

Subtract to find the amount of tax paid:

1890 - 1800 = 90

Divide the amount of tax by the price of the computer:

90 / 1800 = 0.05

Multiply the decimal by 100:

0.05 x 100 = 5%

The tax rate is 5%

the answer is 13

step-by-step explanation:

5*5=25

12*12=144

25+144=169

169^2=13