WASHINGTON — President Donald Trump's plan to overhaul the nation's tax code could provide significant tax cuts for the working-class voters who elected him, but the unknowns could end up hurting many of these core supporters of the president.A look at how Trump's tax plan could affect families at different income levels:THE WORKING CLASSThese are the people who have been left behind by an increasingly globalized economy.Trump's proposal, a one-page outline short on detail, says he would double the standard tax deduction, which could provide significant relief to working-class families. But Trump's top economic adviser used some bad math to describe the proposal, raising questions.Gary Cohn said the standard deduction for a married couple would be doubled to $24,000. But that's not double.