3•[48,5-3•(x-9,6•7,4)]-90,21=9,3
3×[48,5-3×(X-71,04)]-90,21 = 9,3
3×(48,5-3X+213,12)-90,21 = 9,3
3×(48,5-3X+213,12) = 9,3+90,21
3×(48,5-3X+213,12) = 99,51
48,5-3X+213,12 = 99,51:3
48,5-3X+213,12 = 33,17
3X = 48,5+213,12-33,17
3X = 228,45
X = 228,45 : 3
X = 76,15
