5400-50•{84-[45-(7•X-9)•2]}=2250
50×{84-[45-(7·x-9)×2]}=5400-2250
50×{84-[45-(7·x-9)×2]}=3150
84-[45-(7x-9)×2]=3150:50
84-[45-(7x-9)×2]=63
45-(7x-9)×2=84-63
45-(7x-9)×2=21
(7x-9)×2=45-21
7x-9=24:2
7x=12+9
x=21:7
x=3
(a×4+23):7+1=10
a×4+23=(10-1)x7
ax4+23=9x7
ax4=63-23
ax4=40
a=40:4
a=10 nr. ales