= 480/40 =630- 130

= 12 =500

450-225/5+ 135 124*5+ 169/ 13

= 450-45+ 135 =620+ 13

=540 =633

99*425 304+306/ 17-298

=( 100- 1)*425 =304+ 18-298

= 100*425- 1*425 =322-298

=42500-425 =24

=42075

10 1*79-79 (6409+23* 17)/68

=( 10 1- 1)*79 =( 6409+39 1)/68

= 100*79 =6800/68

=7900 = 100

199*490 256*30 1

= (200- 1)*490 = 256*(300+ 1)

= 200*490- 1*490 =256*300+256* 1

=98000-490 =76800+256

=975 10 =77056

16*( 125*34+88* 125)

= 16*[ 125*( 134+88)]

= 16*( 125*222)

= 16* 125*222

=2*(8* 125)*222

=2* 1000*222

=444000

4000/ 125/4/8 999*778+333+666

=(4000*4)*( 125*8) =333*3*778+333* 1+333*2

= 16000* 1000 =333*(778+ 1+2)

= 16000000 =333*78 1

=260073

14*44+ 12*28+32* 14 840*39/84

= 14*44+ 12*2* 14+32* 14 =840/84*39

= 14*(44+24+32) = 10*39

= 14* 100 =390

= 1400

64.68-27.75 24.96+36.78

=36.93 =6 1.74

29.45-(5.55-3.74) 0.76+(45.6-24.7)

=29.45- 1.8 1 =0.76+20.9

=27.64 =2 1.66

0.45+5.7+ 1 1.55+4.3

=(0.45+ 1 1.55)+(5.7+4.3)

= 12+ 10

=22

1. The isosceles triangle has one angle of 60 degrees and the other two angles of 60 degrees. This is an equilateral triangle.

2. The acute angles are 60 degrees and 30 degrees respectively.

3. The third side may be 4, 5, 6, 7, 8, 9, 10,1,12cm.

One angle of a triangle is 50 degrees. It can be an acute triangle, a right triangle or an obtuse triangle.

All three internal angles of an equilateral triangle are 60 degrees.

6. The degrees of two acute angles of an obtuse triangle must be less than 45 degrees.

His other angle is 90 degrees.

8. If the angle 1, the angle 2 and the angle 3 are three internal angles in the same triangle.

(1) angle 1 equals 45 degrees, angle 2 equals 90 degrees and angle 3 equals 45 degrees.

(2) Angle 1 equals 60 degrees, angle 2 equals 80 degrees, and angle 3 equals 40 degrees.