Answer:
(a) A system of equations:

(b) Number of blocks were in the order is, 12
Explanation:
(a)
Let x represents the number of bricks and y represents the number of blocks.
As per the given statement:
A bricks costs $ 0.38 and a block costs $1.56.
Total bricks costs = 0.38x and total block costs = 1.56y
The brickyard filled $24.80 order.
⇒
......[1]
Since, it contained 28 items.
⇒
....[2]
Multiply equation [2] both sides by 0.38 we have;

Using distributive property:

0.38x +0.38 y = 10.64 ......[3]
Subtract equation [3] from [1] to get x eliminated ;
Combine like terms;
1.18y =14.16
Divide both sides by 1.18 we have;

Simplify:

Substitutes this y value in equation [2] to solve for x;
x + 12= 28
Subtract 12 from both sides we get;
x +12-12 =28-12
Simplify:
x = 16
Therefore, a system of equations that can be used to find the number of bricks and the number of blocks in the order:

(b)
The number of blocks are in order(y), is 12.