My question is I am single taxpayer, and I received $6,000 in Social Security benefits. My adjusted gross income for the year was $18,000 not including my social security benefits and I also received $30,000 in tax-exempt interest income what is the amount of Social Security benefits to include in my gross income.

This is from IRS publication:
"To determine whether any of your benefits are taxable, compare the base amount for your filing status with the total of one half of your social security payments plus all your income from other sources, including tax exempt interest."

And your income exceeds the base amount so up to 85% of the benefits may be taxable. It is reported on line 20 of form 1040. You will use Social security Benefits worksheet.

Agreed.