19．63-(2.77 9.63)-0.23
=19.63-(2.77 0.23)-9.63
=19.63-3-9.63
=7
3.5x[(13.4-10.04)/0.1]
=3.5x(3.36/0.1)
=3.5x33.6
=117.6
168-68/25x4
=168-2.75x4
=168-11
=157
9.9x45.5
=(10-0.1)x45.5
=10x45.5-0.1x45.5
=455-4.55
=450.45