We know that for every 5 red bricks there were 2 gray bricks.
The total amount of red bricks and grey bricks in this sample is 7.
5 red bricks + 2 grey bricks = 7 bricks
Now, we divide 175 "total number of bricks used" by 7 "5 red bricks + 2 grey bricks = 7 bricks" and we will get a quotient of 25.
Now we know that 25 bricks is of the wall. The gray bricks are
so we can multiply 25 by 2 and we will get a product of 50. If 1/7 = 25 grey bricks so 2/7 would be the grey bricks.
175 - 50 = number of red bricks.
Therefore, there were 125 red bricks.
