Can she buy enough packs ?

How many tiles does she need ?

1 square meter = 10,000 cm²
12 square meters = 120,000 cm²
Each tile = (20 cm x 20 cm) = 400 cm²
Tiles needed = 120,000 / 400 = 300 tiles

How many tiles can she buy ?

1,000 / 34.99 = 28 boxes, with 20.28 left over . . . not enough for another box.
28 boxes of 10 tiles per box = 280 tiles

Halima doesn't have enough money to buy enough tiles
to cover the wall.  She can only buy 280 tiles, but it would
take 300 to cover the wall.

She can cover 280/300 = 93 and 1/3 percent of the wall,
leaving 6 and 2/3 percent with the old ugly plaster showing.
Maybe she could leave the bare part down at the bottom, and
then hide it with a table up against the wall.