19. Currently, telephone area codes are three-digit numbers whose middle digit must be 0 or 1
Codes whose last two digits are l's are being
used for other purposes, for example, 911. With
these conditions, how many area codes
are
available

Answer: the correct answer is 10step-by-step explanation: let the number be n, then the expression becomes,then“twelve more than the quotient of a number and two, decreased by four” iswhen n=4,we substitute 4 whetever we see n to get,we simplify to obtain,we further simplify to get,therefore the correct answer is c.