. -70 + 20 = ___ - 10

Put the suitable symbol or = in the box: (-20) + 10 ___ (-20) - (-10)

Put the suitable symbol or = in the box: (-70) - (-50) ___ (-70) - 50

Fill in the blanks: (-10) xx __ = 20

Find the value of .^(20)C_(0) xx .^(13)C_(10) - .^(20)C_(1) xx .^(12)C_(9) + .^(20)C_(2) xx .^(11)C_(8) - "……" + .^(20)C_(10) .

Solve, using the method of substitution 10% of x + 20 % of y= 24, 3x - y = 20

Express 45^0 20 ' 10 ' ' in radian measure (pi=3. 1415)

Prove that sin 10° + sin 20° + sin 40° + sin 50°=sin 70° + sin 80