Area of lengthwise 2 walls = \(2( L\times H ) = 2 \times 7 \times x = 14xcm^2\)

Area of breadthwise 2 walls = \(2( B \times H) = 2 \times 5 \times x = 10xcm^2\)

T.S.A of the room( walls only) = \(14xcm^2 + 10xcm^2 = 96cm^2\)

  x = \(\frac{ 96}{14} = 4cm^2\)