Can someone explain substitution more clearly?

As in solving systems by substitution. I'm genuinely stumped, can the process be explained in a coherent and straightforward manner with examples?

The students in the cooking club brought sugar to class. They each brought 3, 4, 5, 3, and 5 cups of sugar, respectively. They divided the sugar evenly so that each student received the same number of cups of sugar.

The area of a rectangular mural is 84square feet. The mural's width is 7 feet. What is its length in feet?

Henry eats 1/3 of a loaf of bread in 2 days. How many loaves of bread will he eat in 12 days?

If a function f (x) has values f (4) = 6 and f (8) = 18, use what you have learned about function patterns to find f (16) = if f (x) is: a.) Linear function: f (16) = b.) Power function: f (16) = c.) Exponential function: f (16) = d.

The cost of 5 shirts and 3 pants is $105.00. Th cost of two shirts is $9.00 more than the cost of one pair of pants. What is the cost of each?

An ottoman in the shape of a cube has a volume of 27 cubic centimeters. What is the surface area of the ottoman? 18 27 54 81

Find m B. Note that m B is acute. Round to the nearest degree.

The sum of a number times 6 and 16 is greater than 22

How many permutations are there of the letters in the word surprise?

Find the x - and y - intercept of the graph of the equation 3x + 4y = 24