700 - x = 56 * 8
700 - x - 700 = 56 * 8 - 700
-x = -252
x = 252
a - 10 = 2352 / 98
98a - 10 * 98= 2352 / 98 * 98
98a - 980 = 2352
98a - 980 + 980 = 2352 + 980
98a = 3332
98a / 98 = 3332 / 98
a = 34
63*(80 - a) = 693
63*(80 - a) / 63 = 693 / 63
80 - a = 11
80 - a - 80 = 11 - 80
-a = -69
a = 69