Răspuns:
a=1753/2
sau
a=1376.5
Explicație pas cu pas:
[(a+428/4)*2+5]/2-186=800
[(a+428/4)*2+5]/2=800+186
[(a+428/4)*2+5]/2=986
(a+428/4)*2+5=986*2
(a+428/4)*2+5=1972
(a+428/4)*2=1972-5
(a+428/4)*2=1967
a+428/4=1967/2
a=1967/2-428/4
a=1967/2-214/2
a=(1967-214)/2
a=1753/2
a=1376.5