Answer:
a) Look step by step explanation
b) x = 498,22
Step-by-step explanation:
a) Two triangles are similar if all their angles are equal
Then in Δ SFH  and  Δ GEL we got:
∡ SFH = ∡ EGL   right angles
∡ LEG = ∡ HSF   since the same straight line (SL) is cut by parallel lines (vertical  segments  EG and SF )
∡ SHF = ∡ ELG  The same straight line SL is cut by two parallel segments FH and GL  ( horizontal segments)
The Δ SIL is similar to the two previous Δs according to:
∡ SIL is a right angle
∡ ILS = ∡ GLE = ∡ FHS
∡ ISL = ∡FSH = ∡GEL
The condition for similar triangles is satisfied
b)
From Δs    FSH and  GEL
SF/EG  = 380/EL
225/180  =  380/EL
225*EL  =  180*380
EL = 180*380/225
EL = 304
From Δs  SIL and SFH
225/ (225 +475)  =  380/ (380 + x + 304)
225 / 700  = 380 / 684 + x
225 * ( 684 + x ) = 700*380
153900 + 225*x = 266000
225*x = 266000 - 153900
225*x = 112100
x = 498,22