Solution Let a, b,c and d go into the boxes respectively as show below. From the row 1 of the diagram, a+b=8--------(1) from column 1 of the diagram, a+c=13-------(2) from row 2 of the diagram, c-d=6--------(3) from column 2 of the diagram, b+d=8------(4) equating (1) and (4) a+b=b+d a=b-b+d therefore, a=d----(5) from equation (2) a=13-c----(6) since a=d, (6) becomes d=13-c c+d=13---(7) solving equation 3 and 7, i.e c+d=13-------(7) c-d=6---------(3) adding equation 7 and 3 above, we have; 2c=19 C=19/2 C=9.5 Substitute the value of c in (7) 9.5+d=13 d=13-9.5 d=3.5 recall that in equation 5, a=d since d=3.5, a=3.5 from equation 4, b=8-d since d=3.5 b=8-3.5 b=4.5 so the numbers that must go inside the boxes are 3.5,4.5,9.5 and 3.5 as shown below Leave a comment and Share to your friends. We do your assignment for free. Send us your mathemati...