a<b; b=c+2=d-3. We need a relationship between a and d. Draw a line on which we are going to mark the points a, b, c and d. Start on the left with points a and b in that order. Where do we put c and d. We see that b is bigger than both a and c, so the order is a-c-b or c-a-b. Now d. We see that b is less than d so the order is a-c-b-d or c-a-b-d. Whichever applies, a<d; a is less than d. In fact, a<d-3.