from the first line: the star and diamond are the same
from the last line: the star multiplied by the diamond is 25
Hence the value of the star is equal to that of the diamond which is the root of 25 = 5
At this point we have:
- star = 5
- diamond = 5
using the above two values, from the second line:
(5+5)+triangle=20
10+triangle=20
triangle=20-10
Triangle = 10
there you have it:)