jacob is now 13 years younger than michael . if 9 years from now michael will be twice as old as jacob , how old will jacob be in 4 years ?
"jacob = x years , michael = x + 13 years 9 years from now , 2 ( x + 9 ) = x + 22 2 x + 18 = x + 22 x = 4 x + 4 = 8 years answer a"
add(4, subtract(add(13, 9), multiply(const_2, 9)))