[1870 - (325 + 5 x a) : 7] - 208 = 52
1870 - (325 + 5 x a) : 7 = 52 + 208
1870 - (325 + 5 x a) : 7 = 260
(325 + 5 x a) : 7 = 1 870 - 260
(325 + 5 x a) : 7 = 1 610
325 + 5 x a = 1 610 x 7
325 + 5 x a = 11 270
5 x a = 11 270 - 325
5 x a = 10 945
a = 10 945 : 5
a = 2 189
