 Word problems on Linear Equation in one variable

Q1) A positive number is 5 times another number. If 21 is added to both the numbers, then one of the new numbers become twice of other new numbers. Find the original numbers.

Q2) The difference between two numbers is 48. The ratio of the two numbers is 7:3. What are the two numbers?

Q3) The length of a rectangle is twice its breadth. If the perimeter is 72 m, find the length and breadth of the rectangle, respectively.

Q4) David cuts a bread into two equal pieces and cuts one half into smaller pieces of equal size. Each of the small pieces is twenty grams in weight. If he has seven pieces of the bread all with him, how heavy is the original cake.

Q5) The distance between two mile stones is 230 km and two cars start simultaneously from the milestones in opposite directions and the distance between them after three hours is 20 km. If the speed of one car is less than that of other by 10 km/h, find the speed of each car.

I am doing Q1 and Q4 and Q5