a,\(\Rightarrow x:3=1,56+7,2\)
\(\Rightarrow x:3=8,76\)
\(\Rightarrow x=8,76\cdot3\)
\(\Rightarrow x=26,28\)
b,\(\Rightarrow x:6=1,248:4\)
\(\Rightarrow x:6=0,312\)
\(\Rightarrow x=0,312\cdot6\)
\(\Rightarrow x=1,872\)
c,(x+x+x+x+...+x)+(2+5+8+....+29)=165
10 số hạng 10 số hạng
\(\Rightarrow\)10x+(29+2)*10:2=165
\(\Rightarrow\)10x+155=165
\(\Rightarrow10x=165-155\)
\(\Rightarrow10x=10\)
\(\Rightarrow x=10:10\)
\(\Rightarrow x=1\)