a)53.25−25.12+75.53 b) \(260 : \left[\right. 5 + 7. \left(\right. 72 : 2^{3} - 6 \left.\right) \left]\right. - 3^{2}\)

=25*41+75*53 =260/[5+7*(9-6)]-9

=1025+3975 = 260/[5+7*3]-9

=5000 = 260/[5+21]-9

=260/26-9

=10-9

=1

b