Draw a small circle on a white sheet of paper. About 6 cm (2 1/2 inches) to the right of this circle, draw a plus-sign, about 3 mm (1/4 inch) in size. Close your left eye and put your nose on the paper so that your right eye is directly above the circle. Slowly move your head up until you cannot see the plus-sign. Measure and record the distance from your eye to the paper. Move your head farther above the paper until the plus-sign reappears. Measure and record this distance. Why does the plus-sign disappear

Ok here we go ..there are plenty of ways to solve such math problems but we will go for the smartest and easiest ..5x+2y=7  -2x+6y=9we rearrange them into the following ..by multiplying the 1st equation by 2 it becomes 10x + 4y = 14we rearrange it and so it becomes 10x = 14 - 4yas for the second equation we multiply it by 5 and rearrange it so it becomes as to the following ..-10x + 30y = 45rearranging so 10x = 30y -45now 10x equals both 14 - 4y and 30y -45so   14 - 4y = 30y -4531 = 26yy= 31/26 = 1.19 or around 1.2so by now we can calculate x easily as  -2x+6y=9so 2x = 6y -9 = 6 * 31/26 - 9 = -1.84  then x = - 0.92 or around -0.9best luck!

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