70 - 5.(x-3) = 45
5.(x-3) = 25
x-3 = 5
x=8
b) 10 + 2x = 45 : 43 = 42 = 16
2x = 6
x = 3
\(70-5\left(x-3\right)=45\)
\(\Rightarrow5\left(x-3\right)=70-45=15\)
\(\Rightarrow x-3=15:5=3\)
\(\Rightarrow x=3+3=6\)
\(10+2x=4^5:4^3\)
\(\Rightarrow10+2x=4^2=16\)
\(\Rightarrow2x=16-10=6\)
\(\Rightarrow x=6:2=3\)