Remember that (a+b)2=a2+2ab+b2. From statement (1), we know that a2+b2=13. By cross multiplying in statement (2), we get 2ab=12. Since we know the values of a2+b2 and 2ab, and (a+b)2=a2+2ab+b2, we can now take the square root of the sum to find the value of a+b.