Нужно найти число возможных звукосочетаний по 3, по 4, ..., по 10 и сложить их.
![C_{10}^3=\frac{10!}{3!*7!}=\frac{8*9*10}{2*3}=4*3*10=120\\C_{10}^4=\frac{10!}{4!*6!}=\frac{7*8*9*10}{2*3*4}=7*2*3*5=210\\C_{10}^5=\frac{10!}{5!*5!}=\frac{6*7*8*9*10}{2*3*4*5}=3*7*2*3*2=252\\C_{10}^6=\frac{10!}{6!*4!}=210\\C_{10}^7=\frac{10!}{7!*3!}=120\\C_{10}^8=\frac{10!}{8!*2!}=\frac{9*10}{2}=9*5=45\\C_{10}^9=\frac{10!}{9!*1!}=10\\C_{10}^{10}=1\\2*120+2*210+252+45+10+1=968](https://tex.z-dn.net/?f=C_%7B10%7D%5E3%3D%5Cfrac%7B10%21%7D%7B3%21%2A7%21%7D%3D%5Cfrac%7B8%2A9%2A10%7D%7B2%2A3%7D%3D4%2A3%2A10%3D120%5C%5CC_%7B10%7D%5E4%3D%5Cfrac%7B10%21%7D%7B4%21%2A6%21%7D%3D%5Cfrac%7B7%2A8%2A9%2A10%7D%7B2%2A3%2A4%7D%3D7%2A2%2A3%2A5%3D210%5C%5CC_%7B10%7D%5E5%3D%5Cfrac%7B10%21%7D%7B5%21%2A5%21%7D%3D%5Cfrac%7B6%2A7%2A8%2A9%2A10%7D%7B2%2A3%2A4%2A5%7D%3D3%2A7%2A2%2A3%2A2%3D252%5C%5CC_%7B10%7D%5E6%3D%5Cfrac%7B10%21%7D%7B6%21%2A4%21%7D%3D210%5C%5CC_%7B10%7D%5E7%3D%5Cfrac%7B10%21%7D%7B7%21%2A3%21%7D%3D120%5C%5CC_%7B10%7D%5E8%3D%5Cfrac%7B10%21%7D%7B8%21%2A2%21%7D%3D%5Cfrac%7B9%2A10%7D%7B2%7D%3D9%2A5%3D45%5C%5CC_%7B10%7D%5E9%3D%5Cfrac%7B10%21%7D%7B9%21%2A1%21%7D%3D10%5C%5CC_%7B10%7D%5E%7B10%7D%3D1%5C%5C2%2A120%2B2%2A210%2B252%2B45%2B10%2B1%3D968)
Ответ: B
5+10=15(земляники)
Ответ: Вера собрала 15 земляники
1300-(d-678)=400(d-678)=1300-400(d-678)=900d=678+900<span>d=157</span>
Числа 25 и 12.
Подробное решение находится в прикрепленном файле.