Please help asap with finding sum of arithmetic sequences

Write two subtraction equations that are equivalent to 5 + 12 = 17.

You use technology ans find a sum of 6.712e-8. write this sum in standard form

An architect builds a model of a park in the shape of a rectangle. the model is 40.64 centimeters long and 66.04 centimeters wide. one inch equals 2.54 centimeters. use the ratio table to find the ratio of the length to the sum of the length and width in inches and in simplest form. length 40.64 width 66.04 a. 8: 21 b. 13: 21 c. 21: 13 d. 21: 8