Question 1
The diagram below shows nine circles joined by seven lines, with three circles on each line. Replace each of $a,b,c,d,e,f,g,h$ and $k$ by a different one of $1,2,3,4,5,6,7,8$ and $9$, such that the number in the middle circle of a solid line is equal to the sum of the numbers in the other two circles, and the number in the middle circle of a dotted line is equal to the difference of the numbers in the other two circles.
Original answer template:
Submission guidance: Supply the completed diagram only. The source does not require a written proof for this odd-numbered question. This graphical response is manually graded, with all-or-nothing credit.
Original answer template:
Submission guidance: Supply the completed diagram only. The source does not require a written proof for this odd-numbered question. This graphical response is manually graded, with all-or-nothing credit.