## Task 1

The members of a youth brigade helped to prepare apartments for elderly citizens. The value amounted to 1200 Marks. They helped with cable installation. This value amounted to 2100 Marks. In the operation, they saved materials. This value amounted to 1500 Marks.

How many Marks did the youth brigade bill for?
$1200+2100+1500=x$. The youth brigade produced 4800 M.