4. (285 + 15):3·5 + 280 400 – (60 + 30): 10 · 1

4.

1. $$285+15=300$$
2. $$300 : 3 = 100$$
3. $$100 \times 5 = 500$$
4. $$500 + 280 = 780$$

4.

1. $$60+30=90$$
2. $$90 : 10 = 9$$
3. $$9 \times 1 = 9$$
4. $$400 - 9 = 391$$

Ответ: 780; 391