The sum is 64 so 64-26=38 is double the smaller number, and that number is 19. The other must be 19+26=45.
Algebraically, if a and b are the numbers and a=b-26 so b-a=26, and a+b=64, then we add these two equations to get 2b=90 so b=45 and a=45-26=19.