1.
6+[15-(8:a*7+7)]*5=8:(1*4)+3*3
6+[15-(8:a*7+7)]*5=8:4+9
6+[15-(8:a*7+7)]*5=2+9
6+[15-(8:a*7+7)]*5=11
[15-(8:a*7+7)]*5=11-6
[15-(8:a*7+7)]*5=5
15-(8:a*7+7)=5:5
15-(8:a*7+7)=1
8:a*7+7=15-1
8:a*7+7=14
8:a*7=14-7
8:a*7=7
8:a=7:7
8:a=1
a=8:1
a=8
2.
5*{55*5-[(55*5-55:5)-55+5]}=
5*{275-[(275-11)-55+5]}=
5*[275-(264-55+5)]=
5*[275-(209+5)]=
5*(275-214)=
5*61=
305
3.
{[(15*10-98):2+76]*110-220}:500=
{[(150-98):2+76]*110-220}:500=
[(52:2+76)*110-220]:500=
[(26+76)*110-220]:500=
(102*110-220):500=
(11 220-220):500=
11 000 : 500 =
22