How do you solve this system by elimination?

-5x+7y=11
-5x+3y=19

i don't know how to solve it.

Students buying lunch at rockwell elementary school yesterday chose either burritos or pizza. 185 students chose burritos and 252 chose pizza. 1. estimate the number of students who brought lunch by rounding each number to the nearest hundred. 2. estimate how many students bought lunch by rounding each number to the nearest ten. 3. find the total number of students who brought lunch. which of your estimates is closer to the actual total? explain. 4. draw a figure on a sheet of paper. estimate how many pennies will fit inside the figure. check your prediction using pennies.

Suppose a pendulum is l meters long. the time,t,in seconds that it tales to swing back and forth once is given by t=2.01

Determine the difference: 3.2 × 1010 – 1.1 × 1010. write your answer in scientific notation.