Arectangle has a width of 12.5 m and a length of 105 m. what is the effect on the perimeter when the dimensions are multiplied by 2?

Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

When you answer this can you explain