a)83-6.(x-7)=35
6(x-7)=83-35=48
x-7=48:6=8
x=8+7=15
b)246+7.(x+15)=442
7(x+15)=442-246=196
x+15=196:7=28
x=28-15=13
c)303:{606:[450-(x.43-83.2)]}=101
606:[450-(x.43-83.2)]=303:101=3
450-(x.43-83.2)=606:3=202
x . 64-512=450-202=248
x . 64=248+512=760
x=760:64=11,875
\(d,\left[196-23\cdot x\right]\cdot3^{2025}=3^{2029}\)
\(\Leftrightarrow\left[196-23\cdot x\right]=3^{2029}:3^{2025}=3^4=81\)
\(\Leftrightarrow196-23\cdot x=81\)
\(\Leftrightarrow23\cdot x=115\Leftrightarrow x=5\)