(5 x 10-1)2

= 98

(5x10 -1)2

Figure out the brackets

5x10= 50-1= 49

then times by two

49x2= 98

(5 x 10-1)2
Actually that's not a good way to express this equation.

The best way:

2(5 x 10 - 1)

= 2 x 5 x 10 - 2

= 100 - 2

= 98

May be you mean (5 x 10 - 1)²?

(5 x 10 - 1)²

=$49^2$

= 2401