(2,61 - 4x) : 0.03 + 4.6 = 90
(2. 6 1 - 4x) : 0.03 = 90 - 4.6
(2.61 - 4x) : 0.03 = 85,4
2.61 - 4x = 85,4 * 0.03
2.61 - 4x = 2,562
4x = 2.61 - 2,562
4x = 0.048
x = 0.048 : 4
x = 0.012
=========
9.54 - 4.74 : (0.3x + 0.49x) = 8.94
4.74 : 0.79x = 9.54 - 8.94
4.74 : 0.79x = 0.6
0.79x = 4.74 : 0.6
0.79x = 7.9
x = 7.9 / 0.79
x = 10