5 x [(85 - 35 : 7) : 8 + 90] - 50
= 5 x [(85 - 5) : 8 + 90] - 50
= 5 x [80 : 8 + 90] - 50
= 5 x [10 + 90] - 50
= 5 x 100 - 50
= 500 - 50
= 450
\(5\times\left[\left(85-35:7\right):8+90\right]-50\\ =5\times\left[\left(85-5\right):8+90\right]-50\\ =5\times\left[80:8+90\right]-50\\ =5\times\left[10+90\right]-50\\ =5\times100-50\\ =500-50=450\)
5 x [(85 - 35 : 7) : 8 + 90] - 50
= 5 x [(85 - 5) : 8 + 90] - 50
= 5 x [80 : 8 + 90] - 50
= 5 x [10 + 90] - 50
= 5 x 100 - 50
= 500 - 50
= 450