1998 Tax Rate Schedule Schedule X - If your filing status is Single 6. In 1989 , a single taxpayer used this 1988 Schedule X. Let x represent the single taxpayer's taxable income and y represent that taxpayer's tax. Express the tax schedule as a piecewise function. f(x)= when x25,350 when 25,350278,450 note: enter expressions with no spaces in this format 3,802.50+28%(x 25,350)