2.875+2.47а+3.27+1.11а=2.875+6.85а=2.875+6.85*0.5=2.875+3.425=6.3

2,875+2,47а+3,27а+1,11а если а=0,5

2,875+2,47*0,5+3,27*0,5+1,11*0,5=2,875+1,235+1,635+0,555=4,11+2,19=6,3