This is an example of systems of equations, using weird symbols rather than x or y.
We'll substitute the symbols for the variables d and c
d for diamond, c for clover.
3 + d = c
c + d = 11
We can solve for one variable in the first equation to find the true value of the other variable in the second equation.
3 + d = c
Subtract 3 from both sides.
d = c - 3
Now we have a value for d and can solve the second equation.
c + d = 11
Substitute.
c + c - 3 = 11
Add 3 to both sides.
c + c = 14
Combine like terms.
2c = 14
Divide both sides by 2.
c = 7
Now we know the absolute value of c and can solve for the value of d.
d + c = 11
d + 7 = 11
Subtract 7 from both sides.
d = 4
The diamond, or d, is equal to 4. And the clover, or c, is equal to 7. (This is your answer.)
Let me know if you have any questions.