## Algebra: A Combined Approach (4th Edition)

x=9 $9 + a = 2 \times 9 - b$ a and b are the blanks $9 + a = 18 - b$ $a + b = 18 - 9$ $a + b = 9$ if you add up the blanks the sum has to be 9 These are all possible equations: 9+8=18-1=17 9+7=18-2=16 9+6=18-3=15 9+5=18-4=14 9+4=18-5=13 9+3=18-6=12 9+2=18-7=11 9+1=18-8=10 9+0=18-9=9