Can someone help me with 10-15 plz

Acomputer store bought a program at a cost of $10 and sold it for $13. find the percent markup

Sundar used linear combination to solve the system of equations shown. he did so by multiplying the first equation by 5 and the second equation by another number to eliminate the y-terms. what number did sundar multiply the second equation by? 2x+9y=41 3x+5y=36

Look at this pattern ; 1,4,9, number 10000 belongs in this pattern . what’s the place of this number?