Hola.
Total : x
Acelgas : 1 / 3
Zanahorias : 3 / 10
Sobra : 110
Sumamos para que nos de la cantidad total :
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B1%7D%7B3%7D.x%2B%20%20%5Cfrac%7B3%7D%7B10%7D.x%2B%20110%3D%20x" />
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7Bx%7D%7B3%7D%20%2B%20%5Cfrac%7B3x%7D%7B10%7D%2B110%3Dx%20" />
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B10x%2B9x%7D%7B30%7D%20%2B%20110%3Dx" />
<img src="https://tex.z-dn.net/?f=%20%5Cfrac%7B19x%2B3300%7D%7B30%7D%20%3Dx" />
<img src="https://tex.z-dn.net/?f=19x%2B3300%3D30x" />
<img src="https://tex.z-dn.net/?f=3300%3D30x-19x" />
<img src="https://tex.z-dn.net/?f=3300%3D11x" />
<img src="https://tex.z-dn.net/?f=x%3D300" />
Rpta : La superficie total es 300m².
Suerte y saludos !