a) 1000 - 107 × ? + 1963 = 2000
1000 + 1963 - 2000 = 107 x X
2963 - 2000 = 107 x X
963 = 107 x X
X = 963: 107
X = 9
b) 7699 + 301: ? - 7998 = 2
301: X = 2 + 7998 - 7699
301: X = 8000 - 7699
301: X = 301
X = 301: 301
X = 1
c) 100 - ? :707 + 38: 2 = 107
100 + 38:2 - 107 = X: 707
100 + 19 - 107 = X: 707
119 - 107 = X: 707
12 = X: 707
X = 707 * 12
X = 8484