STD 10th maths exercise 3.5 elimination method

solve the following pair of equations by cross multiplication method

5x+8y=18
2x-3y=1

The late fee for library books is $2.00 plus 15¢ each day for a book that is late. if maria’s fee for a late book was $3.20, write and solve a linear equation to find how many days late the book was.

Ineeeeed this is due tomorrow and i dont know the answer can you find all the exponents

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?