Help me please to solve this 7. The standard weights (dhaks) and meter scales of the shops in the market are verified in every two years by the department of measurement of Nepal, Why? ​

Nepal bureau of weight and measure, check correctness of the scales and weight used by the general public in the market in every two years because the measuring device may lose their standard due to the regular use and other factors which may bring error in the measurement

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.