Find a8 and an for the arithmetic sequence a10=6 a12=15

Describe the relationship between the angles of similar triangles and the sides of similar triangles

Write the summation to estimate the area under the curve y = 1 + x2 from x = -1 to x = 2 using 3 rectangles and right endpoints

One number is 4 less than 3 times a second number. if 3 more than two times the first number is decreased by 2 times the second number, the result is 11. use the substitution method. what is the first number?