First we solve math inside brackets. They have the highest order.
example: 2+3(5+4)
first we solve 5+4 and than multiply it by 3 and finally add 2
after brackets multiplication and division have highest order. We solve them before we solve summing and subtraction.
3+45 first we do 45
1-5+6/35 here it doesnt matter if we first divide 6 by 3 and than multiply by 5 or we multiply 6 and 5 and than divide by 3. They have same order and result will be the same.
Finaly subtraction and addition is done.
