Between 2000 and 2010, the percentage of households with cordless phones increased by 12.9% to 86%. What percentage of households had cordless phones in 2000

Taking the variable A to be the percentage of households that had cordless phone in 2000, we can set up the equation:

A + (12.9%) A = 86%

where to convert percentage to decimal, divide by 100:

A + 0.129 A = 0.86

Calculating for A:

1.129 A = 0.86

A = 0.86 / 1.129

A = 0.7617

or

A = 76.17%

So around 76.17% in 2000.