a=(0.49-0.6×0.8):0.001-10,5:21×2-2.5=
(0.49-0.48):0.001-10.5:21×2-2.5=
0.01:0.001-10.5:21×2-2.5=
10-0.5×2-2.5=
10-1-2.5=6.5
b=(0.6+0.6):0.1-0.04-3:0.3=
1.2:0.1-0.04-3:0.3=
12-0.04-10=11.96-10=1.96
a) 4a+0.15b=4×6.5+0.5×1.96=26+0.98=26.98
b) 2a-0.1b=2×6.5-0.1×1.96=13-0.196=12.804